Biztalk

50 general interview questions

2014-02-04T03:02:00.000-08:00

What are your strengths?
What are your weaknesses?
Why are you interested in working for [insert company name here]?
Where do you see yourself in five years? 10 years?
Why do you want to leave your current company?
Why was there a gap in your employment between [insert date] and [insert date]?
What can you offer us that someone else cannot?
What are three things your former manager would like you to improve on?
Are you willing to relocate?
Are you willing to travel?
Tell me about an accomplishment you are most proud of.
Tell me about a time you made a mistake.
What is your dream job?
How did you hear about this position?
What would you look to accomplish in the first 30 days/60 days/90 days on the job?
Discuss your résumé.
Discuss your educational background.
Describe yourself.
Tell me how you handled a difficult situation.
Why should we hire you?
Why are you looking for a new job?
Would you work holidays/weekends?
How would you deal with an angry or irate customer?
What are your salary requirements?
Give a time when you went above and beyond the requirements for a project.
Who are our competitors?
What was your biggest failure?
What motivates you?
What’s your availability?
Who’s your mentor?
Tell me about a time when you disagreed with your boss.
How do you handle pressure?
What is the name of our CEO?
What are your career goals?
What gets you up in the morning?
What would your direct reports say about you?
What were your bosses’ strengths/weaknesses?
If I called your boss right now and asked him what is an area that you could improve on, what would he say?
Are you a leader or a follower?
What was the last book you’ve read for fun?
What are your co-worker pet peeves?
What are your hobbies?
What is your favorite website?
What makes you uncomfortable?
What are some of your leadership experiences?
How would you fire someone?
What do you like the most and least about working in this industry?
Would you work 40+ hours a week?
What questions haven’t I asked you?
What questions do you have for me?

Originally published on BusinessNewsDaily.

http://www.sqlservercurry.com/2013/11/sql-server-database-unit-testing-using_16.html

2014-02-04T01:36:00.001-08:00

The core team -Project Management Foundations

2014-01-22T02:04:00.001-08:00

Project Management Foundations - The Core Team

July 8, 2011 | Author: PM Hut | Filed under: Project Management for Beginners

Project Management Foundations - The Core Team
By Steve Hart
At the heart of most successful projects you will find an effective core team that is fully responsible for the day-to-day leadership of the project. This is not to be confused with the strategic level guidance that represents the key function of the project steering committee. The project manager is responsible for ensuring that the core team is effectively selected, on-boarded, and fully engaged throughout the project life cycle.

What Is the Purpose of the Core Team?

The practical answer is that the core team is responsible for monitoring the progress of each of the key deliverables and making decisions about course corrections should the project begin tracking behind schedule, over budget or if major scope changes occur.

What Are the Important Elements of a Good Core Team?

A good core team is comprised of the key stakeholders who are empowered to represent a segment of the overall project domain (the segment is generally defined based upon an organization or competency/function they represent). Representing this segment means that the core team member is responsible for providing knowledge from their area of expertise, and making/influencing decisions that impact this area of expertise. Several key factors influence the process of identifying the core team:

Diversity: Diversity is a key element of the core team, because it is critical that different perspectives about the project and the project deliverables are fairly represented on the core project leadership team. These perspectives should be represented from day one of the core team — many project managers are tempted to exclude groups from the core team until they are needed to perform specific project activities.
Inclusiveness vs. effectiveness: The core team is not the entire project team working on different project activities. Sizing the core team appropriately is critical to the successful management of the project. As the project manager you need to strike a balance between including the right people in the day-to-day management of the project, and creating a team that is too big to effectively make decisions. Based upon my experience the appropriate core team size is somewhere between 6-10 people.
Assessing the Organization: The type of organization you are working in significantly influences the manner in which the core team is formed (depicted in the chart below). In a functional organizational, it is generally the functional leads that represent their area/department on the core team. In a matrix and project organization, the core team is generally formed based upon the role of the people assigned to the project. The type of organization also impacts the project manager’s role and authority on the project (from limited in a functional organization, to full control in a project organization).

Project leadership in different organization types

Procuring the Core Team Members

The factors described above represent key considerations when performing the following steps to select the core team:

Determine which roles should be included on the core team. I find the most effective method is to look for the roles on the RACI chart with the most significant R’s (Responsible).
Decide what project team members can fulfill these roles, If the team has not been formed, the question becomes what people in the organization can fulfill these roles.
Determine if the composition of the core team needs to be adjusted based upon disconnects between the roles on the core team and the names assigned to the team.

The following chart provides an example of assembling a core team, based upon ownership of the key project deliverables. Ownership does not necessarily represent the person that will complete or manage the deliverable, but rather the person that will be responsible for the deliverable. Responsible means that this is the role that will ensure that the quality, scope, timing and cost of the deliverable are satisfied based upon the expectations established in the baseline project plan. Key deliverables which do not have an explicit owner established on the core team generally represents a RED flag (project risk), because the project manager will likely be required to manage these deliverables outside of the project leadership team as a “one off” process.

Core team example
You will find that multiple people may be required to fulfill specific roles, if one person cannot adequately represent the full scope of the deliverable on the core team. In addition, specific roles may be filled by consultants or third party partners.
Getting stakeholders, functional managers and other resource managers to agree to loan you the right resources for your core team can be a challenge. Having a solid project management plan with high level milestones and roles/responsibilities, Project Sponsor support for the initiative, and clear definition of the deliverables (in the form of a WBS) to reference during the discussion with the resource managers makes this process much easier. When assembling the core team it is important to interact with the potential core team members to understand how well they understand the project – and how they feel about the business case (benefits, scope, target dates). It is a bonus to obtain resources that are passionate about some aspect of the initiative (benefits to their organization, learning opportunities for them, team dynamics).

On-boarding the Core Team

Prior to the overall project kick-off, the core team is assembled for a planning meeting (or series of planning meetings, depending on the complexity of the project). The planning meeting helps level set the core team on project planning efforts that have been completed to date (prior to them joining the team), and launching the efforts to complete the remaining planning activities/deliverables. The Project Manager facilitates the discussion on project planning deliverables completed to-date (project charter, milestones/target dates, scope statement, RACI, and the Project Management Plan). Making sure everyone is clear about what their role on the project is one of the essential topics at this point in forming the core team.
The Core Team planning meeting is best structured in the following manner:

Goals and objectives
- Communicate information about the project using project artifacts created to-date
- Establish a common understanding of roles and responsibilities
- Begin the process of completing the remaining planning deliverables
Activities / Discussion Topics
- Icebreakers and introductions (particularly important for new projects, with a diverse cross-functional team)
- Review of project deliverables (best to provide access to these deliverables in advance of the meeting, so this time is spent productively covering questions and open issues)
- Establish core team priorities and begin working on the remaining planning deliverables

Core Team Best Practices

The following summarizes the best practices associated with selecting, procuring, and on-boarding your core project team:

Purposefully select the core team
- The team’s diversity in terms of backgrounds, perspectives and talents significantly improves project outcomes.
- Right-size the team to accomplish the task at hand – manage the day-to-day project operations. Make sure the team can adequately “own” the project deliverables, but is not too large to effectively manage team dynamics.
- The core team should be formed in a manner that is consistent with the organization that is driving the project.
Work with the right people to procure the right team members
- Clearly communicate with resource managers (about the project and resource needs).
- Use the project sponsor appropriately to gain support of the initiative.
- Obtain buy-in of the potential core team members (to understand their commitment to the initiative, and comfort with their role).
Make the effort to adequately on-board and ramp-up the core team
- Spend time “forming” the team.
- Clearly communicate the plans completed to-date. You want the core team to “own” the plans, even if they were not involved in making all of the decisions or creating all of the planning deliverables.
- Focus on getting immediate traction on the work ahead. Quickly align the core team with the project priorities, and ownership of next steps.

The Project Design Master Class -PMP

2014-01-22T02:02:00.000-08:00

Overview

Much as you to design the software system, you must design the project: from accurately calculating the planned duration and cost, to devising several good execution options, scheduling resources, and even validating your plan, to ensure it is sensible and feasible. This requires understanding the inner dependencies between services and activities, the critical path of integration, the staff distribution and the risks involved. All of these challenges stem from your system design and addressing them properly is a hard core engineering task – designing the project. This design task requires both the project manager and the architect to work closely together to determine the best overall plan.

The Project Design Master Class will take you to a new level as project managers and architects. The class shares IDesign's original battle proven techniques and methodologies that so far have only been the privilege of IDesign's direct customers. You will master the core body of knowledge and skills required of modern software project design. IDesign will mentor you how to gain credibility and perfect communication with top management by providing real life, repeatable and workable options for the project - solutions that balance cost, schedule and risk. Practicing our techniques feels as if "the blinders are off", enabling you to mechanize most aspects of project design while relaying on the IDesign Method and making the most of other tools.

Assuming no prior knowledge, the class covers the essentials of the critical path method, a technique admirably suited for complex software systems and arguably, the only one that works. By modeling the project as a network you eliminate the bias and objectively calculate schedule and cost. You will understand the typical behavior of a project, how it is affected by limiting resource and schedule, and what recurring techniques and approaches to leverage as you cope with constraints.

With these basics in place, you will proceed to see the IDesign Method approach for project design, which enables you to determine the best overall plan across architecture, schedule, cost and risk. The IDesign Method for project design converges on the best and even optimal solution for the project while eliminating gambling, death marches, wishful thinking, and expensive trial and errors. Next the class discussed some advanced project design techniques such as the project time-cost curve, schedule acceleration with network compression and crashing, and IDesign's original risk quantifying techniques. Since there are several design solutions for every project, some more aggressive than others, you must objectively measure the risk of each option and evaluate the project design solutions in light of risk as well as cost and duration.

But no project plan survives unscathed the first day of execution – priorities, resources, deadlines, estimations and features will change, and you must constantly adapt the plan for the new reality. The class will show you IDesign's techniques for closing the loop by tracking both progress and effort across developers and services and containing the impact of changes, allowing you to constantly stay on schedule and on budget.

The class ends with a comprehensive case study and walks through its various permutations in determining the best plan that will keep the project on time all the time at the best risk and cost available. Moreover, the case study not only demonstrates end-to-end flow of project design across iterations, but it also demonstrates the thought process and rationale behind the decisions, our practical approach for using tools, how to integrate and compensate for their shortcomings and utilizing the IDesign templates.

While most training classes merely stack modules, focusing on a single topic at a time, the Project Design Master Class uses a spiral, and each iteration gains more insight across multiple topics, providing the motivation and objectives for next iteration, thus mimicking the natural learning process. Each such iteration incorporates hands-on labs to cement the concepts and practice the techniques. In the class you will also receive the IDesign's original tools, metrics, thumb rules, project design templates, and reference projects.

Don’t miss on this unique opportunity to learn and improve your project design skills with IDesign, and share our passion for excellence and project engineering, gain from our extensive experience of numerous projects design and profound insight on architecture, the process and its application.

While the class will open new horizons for you about project design and the possibilities, we recognize you often need to educate others even on the basics. You may find our project design call for action instrumental in getting support for transforming your environment.

Target Audience

Any project manager, architect, development manager or even aspiring senior developer wanting to grow their skill set would benefit greatly from the class. The class's specific objective is to train the project manager and the architect of the same solution to work together synergistically, so it is particularity suited for such a pair to attend together.

Duration

5 very challenging days.

Outline

Project Design Method Overview

The core team
Development plan
Product life cycle
Service life cycle
Estimations techniques
Services integration plan
Staffing distribution
Scheduling activities
Viability and risk
Figuring cost
Tracking progress and effort
Roles and responsibilities

Essential Concepts

Project as a network diagram
Node vs. arrow diagrams
Critical path pre-requisites
Identifying critical path
Calculating floats
Floats and scheduling
Proactive risk management

Project Compression

Time-Cost curve
Points on Time-Cost curve
Solutions and feasibility
Cost elements
Staffing and cost
Critical path compression
Activity crashing
Project crashing

Quantifying Risk

Risk curve
Risk and floats
Modeling risk
Criticality risk index
Activity Risk index
Exponential risk behavior
Risk decompression
Tracking risk

Project Design in Action

Architecture and dependencies
Complexity reduction
Adding activities
Fuzzy front end
Tools and network diagram
Working with/around MS-Project
Abstracting network diagram
Staffing requirements
Planning assumptions
Network and resources
Staffing distribution
Floats analysis
Infrastructure and dependencies
Design with limited resources
Design with sub-critical resources
Milestones identification
Project compression and crashing
Accelerating schedule
Team throughput analysis
Building and modeling Time Cost curve
Quantifying Risk
Risk decompression
Planning and risk

Project Design Mini-Clinic

Project walkthrough
Planning assumptions
Normal solution
SDP presentations and review

practice interview questions 2

2013-10-11T02:48:00.000-07:00

http://www.hanselman.com/blog/BuildingWebAppsWithASPNETJumpStart8HoursOfFREETrainingVideos.aspx

I do a LOT of interviewing here, and for a while we were hiring ASP.NET people. Here's some of the questions that I asked them. I came up with these questions because you'd "just know" this stuff if you spent time working on a REAL WORLD ASP.NET site - through design, development, debugging, production debugging, and deployment.

Do they suck? Did I miss any? How do you think people did?

From constructor to destructor (taking into consideration Dispose() and the concept of non-deterministic finalization), what the are events fired as part of the ASP.NET System.Web.UI.Page lifecycle. Why are they important? What interesting things can you do at each?
What are ASHX files? What are HttpHandlers? Where can they be configured?
What is needed to configure a new extension for use in ASP.NET? For example, what if I wanted my system to serve ASPX files with a *.jsp extension?
What events fire when binding data to a data grid? What are they good for?
Explain how PostBacks work, on both the client-side and server-side. How do I chain my own JavaScript into the client side without losing PostBack functionality?
How does ViewState work and why is it either useful or evil?
What is the OO relationship between an ASPX page and its CS/VB code behind file in ASP.NET 1.1? in 2.0?
What happens from the point an HTTP request is received on a TCP/IP port up until the Page fires the On_Load event?
How does IIS communicate at runtime with ASP.NET? Where is ASP.NET at runtime in IIS5? IIS6?
What is an assembly binding redirect? Where are the places an administrator or developer can affect how assembly binding policy is applied?
Compare and contrast LoadLibrary(), CoCreateInstance(), CreateObject() and Assembly.Load().

A while back, I posted a list of ASP.NET Interview Questions. Conventional wisdom was split, with about half the folks saying I was nuts and that it was a list of trivia. The others said basically "Ya, those are good. I'd probably have to look a few up." To me, that's the right response.

Certainly I wasn't trying to boil all of .NET Software Development down to a few simple "trivia" questions. However, I WAS trying to get folks thinking. I believe that really good ASP.NET (and for that matter, WinForms) is a little [read: lot] more than just draging a control onto a designer and hoping for the best. A good race driver knows his car - what it can do and what it can't.

So, here's another list...a greatly expanded list, for your consumption (with attribution). I wrote this on a plane last week on the way from Boise to Portland. I tried to take into consideration the concerns that my lists contain unreasonable trivia. I tried to make a list that was organized by section. If you've never down ASP.NET, you obviously won't know all the ASP.NET section. If you're an indenpendant consultant, you may never come upon some of these concepts. However, ever question here has come up more than once in the last 4 years of my time at Corillian. So, ~~knowing~~ groking these questions may not make you a good or bad developer, but it WILL save you time when problems arise.

What Great .NET Developers Ought To Know

Everyone who writes code

Describe the difference between a Thread and a Process?
What is a Windows Service and how does its lifecycle differ from a "standard" EXE?
What is the maximum amount of memory any single process on Windows can address? Is this different than the maximum virtual memory for the system? How would this affect a system design?
What is the difference between an EXE and a DLL?
What is strong-typing versus weak-typing? Which is preferred? Why?
Corillian's product is a "Component Container." Name at least 3 component containers that ship now with the Windows Server Family.
What is a PID? How is it useful when troubleshooting a system?
How many processes can listen on a single TCP/IP port?
What is the GAC? What problem does it solve?

Mid-Level .NET Developer

Describe the difference between Interface-oriented, Object-oriented and Aspect-oriented programming.
Describe what an Interface is and how it’s different from a Class.
What is Reflection?
What is the difference between XML Web Services using ASMX and .NET Remoting using SOAP?
Are the type system represented by XmlSchema and the CLS isomorphic?
Conceptually, what is the difference between early-binding and late-binding?
Is using Assembly.Load a static reference or dynamic reference?
When would using Assembly.LoadFrom or Assembly.LoadFile be appropriate?
What is an Asssembly Qualified Name? Is it a filename? How is it different?
Is this valid? Assembly.Load("foo.dll");
How is a strongly-named assembly different from one that isn’t strongly-named?
Can DateTimes be null?
What is the JIT? What is NGEN? What are limitations and benefits of each?
How does the generational garbage collector in the .NET CLR manage object lifetime? What is non-deterministic finalization?
What is the difference between Finalize() and Dispose()?
How is the using() pattern useful? What is IDisposable? How does it support deterministic finalization?
What does this useful command line do? tasklist /m "mscor*"
What is the difference between in-proc and out-of-proc?
What technology enables out-of-proc communication in .NET?
When you’re running a component within ASP.NET, what process is it running within on Windows XP? Windows 2000? Windows 2003?

Senior Developers/Architects

What’s wrong with a line like this? DateTime.Parse(myString);
What are PDBs? Where must they be located for debugging to work?
What is cyclomatic complexity and why is it important?
Write a standard lock() plus “double check” to create a critical section around a variable access.
What is FullTrust? Do GAC’ed assemblies have FullTrust?
What benefit does your code receive if you decorate it with attributes demanding specific Security permissions?
What does this do? gacutil /l | find /i "Corillian"
What does this do? sn -t foo.dll
What ports must be open for DCOM over a firewall? What is the purpose of Port 135?
Contrast OOP and SOA. What are tenets of each?
How does the XmlSerializer work? What ACL permissions does a process using it require?
Why is catch(Exception) almost always a bad idea?
What is the difference between Debug.Write and Trace.Write? When should each be used?
What is the difference between a Debug and Release build? Is there a significant speed difference? Why or why not?
Does JITting occur per-assembly or per-method? How does this affect the working set?
Contrast the use of an abstract base class against an interface?
What is the difference between a.Equals(b) and a == b?
In the context of a comparison, what is object identity versus object equivalence?
How would one do a deep copy in .NET?
Explain current thinking around IClonable.
What is boxing?
Is string a value type or a reference type?
What is the significance of the "PropertySpecified" pattern used by the XmlSerializer? What problem does it attempt to solve?
Why are out parameters a bad idea in .NET? Are they?
Can attributes be placed on specific parameters to a method? Why is this useful?

C# Component Developers

Juxtapose the use of override with new. What is shadowing?
Explain the use of virtual, sealed, override, and abstract.
Explain the importance and use of each component of this string: Foo.Bar, Version=2.0.205.0, Culture=neutral, PublicKeyToken=593777ae2d274679d
Explain the differences between public, protected, private and internal.
What benefit do you get from using a Primary Interop Assembly (PIA)?
By what mechanism does NUnit know what methods to test?
What is the difference between: catch(Exception e){throw e;} and catch(Exception e){throw;}
What is the difference between typeof(foo) and myFoo.GetType()?
Explain what’s happening in the first constructor: public class c{ public c(string a) : this() {;}; public c() {;} } How is this construct useful?
What is this? Can this be used within a static method?

ASP.NET (UI) Developers

Describe how a browser-based Form POST becomes a Server-Side event like Button1_OnClick.
What is a PostBack?
What is ViewState? How is it encoded? Is it encrypted? Who uses ViewState?
What is the <machinekey> element and what two ASP.NET technologies is it used for?
What three Session State providers are available in ASP.NET 1.1? What are the pros and cons of each?
What is Web Gardening? How would using it affect a design?
Given one ASP.NET application, how many application objects does it have on a single proc box? A dual? A dual with Web Gardening enabled? How would this affect a design?
Are threads reused in ASP.NET between reqeusts? Does every HttpRequest get its own thread? Should you use Thread Local storage with ASP.NET?
Is the [ThreadStatic] attribute useful in ASP.NET? Are there side effects? Good or bad?
Give an example of how using an HttpHandler could simplify an existing design that serves Check Images from an .aspx page.
What kinds of events can an HttpModule subscribe to? What influence can they have on an implementation? What can be done without recompiling the ASP.NET Application?
Describe ways to present an arbitrary endpoint (URL) and route requests to that endpoint to ASP.NET.
Explain how cookies work. Give an example of Cookie abuse.
Explain the importance of HttpRequest.ValidateInput()?
What kind of data is passed via HTTP Headers?
Juxtapose the HTTP verbs GET and POST. What is HEAD?
Name and describe at least a half dozen HTTP Status Codes and what they express to the requesting client.
How does if-not-modified-since work? How can it be programmatically implemented with ASP.NET?
Explain <@OutputCache%> and the usage of VaryByParam, VaryByHeader.
How does VaryByCustom work?
How would one implement ASP.NET HTML output caching, caching outgoing versions of pages generated via all values of q= except where q=5 (as in http://localhost/page.aspx?q=5)?

Developers using XML

What is the purpose of XML Namespaces?
When is the DOM appropriate for use? When is it not? Are there size limitations?
What is the WS-I Basic Profile and why is it important?
Write a small XML document that uses a default namespace and a qualified (prefixed) namespace. Include elements from both namespace.
What is the one fundamental difference between Elements and Attributes?
What is the difference between Well-Formed XML and Valid XML?
How would you validate XML using .NET?
Why is this almost always a bad idea? When is it a good idea? myXmlDocument.SelectNodes("//mynode");
Describe the difference between pull-style parsers (XmlReader) and eventing-readers (Sax)
What is the difference between XPathDocument and XmlDocument? Describe situations where one should be used over the other.
What is the difference between an XML "Fragment" and an XML "Document."
What does it meant to say “the canonical” form of XML?
Why is the XML InfoSet specification different from the Xml DOM? What does the InfoSet attempt to solve?
Contrast DTDs versus XSDs. What are their similarities and differences? Which is preferred and why?
Does System.Xml support DTDs? How?
Can any XML Schema be represented as an object graph? Vice versa?

« LogZipper.NET Log File Rotation | Blog Home | Confusion in Charlotte and an Apology »

ABOUT SCOTT

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. I am a failed stand-up comic, a cornrower, and a book author.

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practice interview questions

2013-10-11T02:43:00.001-07:00

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New Interview Questions for Senior Software Engineers

February 17, '11 Comments [158] Posted in Learning .NET | Programming

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Thursday, February 17, 2011 7:34:29 PM UTC

What is the difference between TDD and BDD?

Zubair Ahmed

Thursday, February 17, 2011 7:36:45 PM UTC

One I generally like is:

Name three primary attributes of object-oriented design. Describe what they mean and why they're important.

It amazes me how so many developers out there think that OO is nothing more than "classes with methods/members on them" and maybe "inheritance for sharing functionality." Also, I've found myself in some really interesting conversations with good developers on this subject. It segues pretty well into other topics too, such as some SOLID principles and interfaces.

David Donahue

Thursday, February 17, 2011 7:38:09 PM UTC

Whenever I ask an about patterns in an interview 95% of the candidates will answer with the factory pattern. Ask them to describe a pattern that is NOT the factory pattern. (i.e. Decorator/Strategy/etc... ). This is where you will find most of the junior engineers will not be able to identify another pattern.

Thursday, February 17, 2011 7:38:13 PM UTC

Why is the phrase "being like Hanselman" considered a compliment?

Haddicus

Thursday, February 17, 2011 7:39:51 PM UTC

You have just been put in charge of a legacy code project with maintainability problems. What kind of things would you look to improve to get the project on a stable footing?

KevDog

Thursday, February 17, 2011 7:40:03 PM UTC

Most of the questions here and on the other posts you referred to are great for gauging competency. Overall they're pretty similar to questions I've been asked when I applied a Microsoft and other companies.

The one challenged I've had is that a lot of these concepts weren't covered in my college courses and many of these concepts haven't really come up in my career as a developer. Do you have any good recommendations for resources to learn more about these topics? I'd like to expand my horizons, but it's often tough to find articles and resources that focus on concepts rather than implementations.

Ian

Thursday, February 17, 2011 7:41:10 PM UTC

While I had used most of these patterns at one time or another (and many of them I had discovered on my own in struggling through design problems), it wasn't until fairly recently that I learned that they had names. I recommend being careful not to quiz interviewees on specific patterns by name, and instead focus on their ability to problem solve. For example, give them a scenario when inversion of control might be needed, and see how they reason through it.

Dale Barnard

Thursday, February 17, 2011 7:41:24 PM UTC

I'm not to keen on the anti-pattern question. Anti-patterns can be patterns in certain contexts and the other way around. I think I would only be able to come up with two anti patterns in an interview, service locator and singleton. Both of these patterns has valid use cases.

Patrik Hägne

Thursday, February 17, 2011 7:41:28 PM UTC

I got asked the last one at an interview today, and it was for a junior position. Caught me out completely, so it's most likely a good question to ask.

I'm poor at remembering theory. Advantages and disadvantages etc, purpose of things, sometimes interviews are a nightmare!

Andy

Thursday, February 17, 2011 7:42:51 PM UTC

Show me a portfolio of all the applications you worked on, and tell me how you contributed to design them. Isn't it the only question that really matters?

David Brabant

Thursday, February 17, 2011 7:44:54 PM UTC

Ian - Awesome question. I'm going to think about this and how it can be done.

Scott Hanselman

Thursday, February 17, 2011 7:46:00 PM UTC

Patrik - I agree with your point, but I also think it's worth having those kinds of discussions. I would say there is no right or wrong answer for some of these.

Scott Hanselman

Thursday, February 17, 2011 7:48:56 PM UTC

Could not agree more with David !
And based on _that_ answer you can start digging for things like patterns etc ... the person used during these projects.

Bart De Keersmaeker

Thursday, February 17, 2011 7:49:56 PM UTC

What are some alternate ways to store data other than a relational database? Why would you do that, and what are the trade-offs?

jarodf

Thursday, February 17, 2011 7:51:45 PM UTC

I fail to see the relevancy of a 70's rock band to programming http://www.gangoffour.co.uk - I'm afraid I lose here :)

hugoware.myopenid.com

Thursday, February 17, 2011 7:52:06 PM UTC

Explain the concept of convention over configuration, and talk about an example of convention over configuration you have seen in the wild.

Explain the differences between stateless and stateful systems, and impacts of state on paralellism.

Discuss the differences between Mocks and Stubs/Fakes and where you might use them (answers aren't that important here, just the discussion that would ensue).

Discuss the concept of YAGNI and explain something you did recently that adhered to this practice.

Explain what is meant by a sandbox, why you would use one, and identify examples of sandboxes in the wild.

bittercoder

Thursday, February 17, 2011 7:53:06 PM UTC

David has a great point. I've long said that rather than certifications and degrees after our names, we should put projects.

Signed,
Scott Hanselman, 23 successful projects, 3 failed

Scott Hanselman

Thursday, February 17, 2011 7:53:55 PM UTC

Bittercoder - I love these.

Scott Hanselman

Thursday, February 17, 2011 7:56:39 PM UTC

1) Can you explain orthogonality, cohesion, and coupling as related to OOD. How much, or little, of each would you want in a system/class?

2) Can you explain the difference between essence and ceremony?

3) Can you explain convention over configuration? Can you give an example of it in action?

Darrell Mozingo

Thursday, February 17, 2011 7:57:00 PM UTC

I think design exercises are a lot more useful than rote answers. You don't really care if someone knows the difference between DI and IoC, do you? Or listing the attributes of OOD? Maybe you do, I'm not sure I see value there. What's useful to me is to see how they apply relevant principles in the moment.

Good interview questions are really hard to come by. Good luck!

Dave

Thursday, February 17, 2011 7:58:56 PM UTC

@Ian - Check out the book "Head First Design Patterns". It's probably the most approachable guide to helping one grok design patterns. It also covers, quite nicely, design principles.

Jonmichael Presley

Thursday, February 17, 2011 7:59:02 PM UTC

1.are you still writing code? Do you love it?
2. You've just been assigned to a project in a new technology how would you get started?

Roi Paul

Thursday, February 17, 2011 8:00:47 PM UTC

You might want to ask some questions about concurrency. What's the difference between Locking and Lockless concurrency models? What kinds of problems can you hit with locking model? And a lockless model? What trade offs do you have for resource contention? How might a task-based model differ from a threaded model? What's the difference between async and concurrency, if any?

And you might ask some questions with more of a functional spin. What does composition mean in an OO and a functional context? What's the difference between a function and a predicate?

Matthew Adams

Thursday, February 17, 2011 8:02:06 PM UTC

Another thought: it's easier than you think to BS these kinds of questions, especially at senior levels. There's no substitute for having someone write actual code in an interview. If you haven't been doing this, you would probably be surprised at how many "programmers" this catches.

Also, this might be useful: http://sites.google.com/site/steveyegge2/five-essential-phone-screen-questions

Dave

Thursday, February 17, 2011 8:07:26 PM UTC

I think these are MUCH better than the old questions. If someone can answer all of these, you can probably assume they know how to look up API documentation for framework specific problems.

I might add something about incorporating SOA/data services/etc into application design and when is it appropriate.

Jason Gerstorff

Thursday, February 17, 2011 8:09:16 PM UTC

1) Explain the concepts of coupling and cohesion and how they relate to maintainability. As a follow up, please explain afferent coupling and efferent coupling, and how those concepts fit above.

Steven Proctor

Thursday, February 17, 2011 8:09:36 PM UTC

Roi - Love those!

Scott Hanselman

Thursday, February 17, 2011 8:11:18 PM UTC

Dave - Is the abilty to BS these questions a problem with the interviewee or the interviewer?

Scott Hanselman

Thursday, February 17, 2011 8:17:32 PM UTC

Roi paul question number one is awesome!!! I saw so many "consultant" minimizibg the importance of tech aspects and how many failing project due to requirements gathered from those "consultants"!

Gianluca

Thursday, February 17, 2011 8:18:01 PM UTC

Am I the only developer that doesn't know everything? Most of these questions I have no clue the answer. Or are programmers just so "smart" that we expect every developer to know everything?

I consider myself a very good developer. Maybe I'm just not "senior" enough...

How many of these questions would you expect a candidate to answer correctly?

bobbycannon.myopenid.com

Thursday, February 17, 2011 8:18:45 PM UTC

Scott,

The projects after the name may be good for a role like this, but for someone just starting out it's going to be a little difficult. :)

Another pretty horrific question I got today was basically, the interviewer wrote some code on the board, and I basically had to describe the state of the stack and the heap after each line of code. I guess to demonstrate an underlying knowledge of the technology.

How many people would actually be able to do that, without having to read up to refresh their memory first? Genuinely curious.

Andy

Thursday, February 17, 2011 8:19:03 PM UTC

Many of these questions are so abstract that it's hard to say whether they predict actual job performance. I can answer most if not all of them, but I never encounter them asked in such an open-ended fashion in my daily work.

I second the vote for giving them a keyboard and actually watching them program. Pair program, if possible.

Failing that, hand the candidate a printout of actual code, in a language she'll be working in if hired. Have her code-review it. You can seed it with a range of problems: say, unchecked nulls, uninitialized collections, publicly mutable fields, to more subtle and arguable things like a function with multiple exit points, or a call to a virtual member from the constructor.

Also, even though I'm mostly against definitional questions in interviews, I'd expect a senior dev to be able to define cyclomatic complexity.

Mark Knell

Thursday, February 17, 2011 8:19:46 PM UTC

Ian - A number of those initial questions are described in Uncle Bob's book
Agile Principles, Patterns, and Practices in C# which I believe is a updated version of Agile Software Development, Principles, Patterns, and Practices originally written for Java. I would strongly recommend Agile Principles, Patterns, and Practices in C# as a good read if you do object oriented development. Even if you have been doing OO for some years I have found it a good as a reference book to go back to occasionally and get refreshed on the concepts.

Steven Proctor

Thursday, February 17, 2011 8:19:48 PM UTC

Another one that I think you might appreciate:

"Tell me about 3 times you failed"

:)

Rob Conery

Thursday, February 17, 2011 8:21:29 PM UTC

@Jonmichael - That book is actually sitting on my nightstand. It has been very helpful and I actually found that I already knew some of the concepts, just not their official names. It was also enlightening to see how similar Java and C# are. I've found there are many more resources that focus on Java rather than C#.

Ian

Thursday, February 17, 2011 8:22:17 PM UTC

@Steven Thanks for the recommendation. That book is ordered and on it's way.

Ian

Thursday, February 17, 2011 8:23:37 PM UTC

@Mark Knell - I like your style however a lot of those issues are basic programming issues. As I type that I had a thought that these are the majority of the problems that riddle our software. Sometimes I feel that we (programmers) forget some of the basics because it's "boring".

bobbycannon.myopenid.com

Thursday, February 17, 2011 8:27:48 PM UTC

What do you do to stay abreast of the latest technologies and tools?

Do you read other peoples code on a regular basis? What is the last open source project you read?

What is your preferred programming language/platform? Why do you prefer it over others? Also, what don't you like about that language/platform?

What is the last programming book you read?

If you were required to look into and learn about a new platform/technology/language to get an understanding of what it would take to get the dev team started with it, what would you do?

--
Who really cares how much someone knows, if they don't do much to keep learning more? You also need to get an idea of how they think or approach a problem.

Thursday, February 17, 2011 8:36:02 PM UTC

Don't look at these questions as interview questions. For developers not looking for a new gig, this is a great post to brush up on those ideas that you don't know, or may have forgotten.

Adamo Mosca

Thursday, February 17, 2011 8:39:01 PM UTC

If all of those questions are related to .Net developments so I'm not a developer :) are we getting the answers soon?

Ahmed Magdy

Thursday, February 17, 2011 8:39:27 PM UTC

Yikes, looks I need to do my homework. I'm not able to answer a handful of these and I consider myself a senior developer. I've got 2 MCPD's and have written for MSDN magazine.

Adam Miller

Thursday, February 17, 2011 8:39:42 PM UTC

Good questions! How about this one to get a conversation going.

Describe to me some bad code you've read or inherited lately.
Can you describe some code smells?

Kenny

Thursday, February 17, 2011 8:40:51 PM UTC

Scott...

>What's the difference between Locking and Lockless concurrency models?

I assume you are asking about Optimistic and Pessimistic concurrency here? If not, what is that above... I don't think I've heard those terms... I pretty much "think" I could give pretty good answers for all of the rest.

BOb

PilotBob

Thursday, February 17, 2011 8:42:45 PM UTC

It's a problem with neither participant, rather it's a problem with (some of) the questions. They don't test what you really value, which is the ability to write good code, and to make good design choices in the moment. Not whether they know the methodology acronym of the day. It's a difference between knowing and doing, between being an advanced novice and being an expert. On the other hand, these are likely to be the questions he will face, so it's good for him to be ready for them.

BTW, I find Singleton to be the most often quoted (and usually misapplied) pattern. Interesting that you zeroed in on Factory.

In addition to interview practice, which is a good idea, I'd advise your friend to get busy with a project (possibly open source). It will keep his chops up, and is a great opportunity to learn something new. It also makes a fantastic story to tell a potential employer (and would provide a good context for answering these kinds of questions).

Dave

Thursday, February 17, 2011 8:45:16 PM UTC

Describe a pattern that is NOT the Factory Pattern?

9 out of 10, when I ask for known patterns, I get Singleton and Factory, and only these two. Usually without the distinction between Factory Method and Abstract Factory.

grootjans

Thursday, February 17, 2011 8:46:33 PM UTC

Describe an interesting problem that you solved recently. What ideas and considerations did you personally bring to the solution? I find this is a good springboard into areas where the candidate will be able to talk passionately and avoid just fumbling with buzzwords.

What is deferred execution? What role does it play in stateless/stateful systems?

Describe a situation where contract first design is beneficial. Discuss a situation where it is not.

When should a server technology dictate storage mediums? When are there good cases for a client to specify how/where/when their data is stored.

Great thread. Thank you so much for starting this.

Stuart Thompson

Thursday, February 17, 2011 8:46:57 PM UTC

Yes sure for your friend.. :)

Edward

Thursday, February 17, 2011 8:51:37 PM UTC

I think more important than the question is the context in which it is applied. Asking a laundry list of questions is more an exercise of endurance than a conversation between two developers. I prefer conversation, so when I interview a developer I send him to the board and ask him to describe the architecture of his last project.

With that framework in place, both the developer and I get to talk about principles and patterns in a more meaningful way. The developer gets a chance to show me what he knows in a practical manner. More importantly, I get to see how the developer communicates on his feet.

TVD

Thursday, February 17, 2011 8:58:27 PM UTC

I thought I was a decent .NET developer, but a good number of these questions will cause me to resort to googling! Any way to get some short answers to them posted in a future blog?

Thursday, February 17, 2011 9:01:51 PM UTC

It's scary when you know the answer but not the terminology that is being used in the question.

That said, I might ask:

- Left to your own devices, what would you create?
- What elements of OO design are most prone to abuse? How would you mitigate that?
- Why might it be bad to "burn the base class"?

Jeff Yates

Thursday, February 17, 2011 9:03:39 PM UTC

When do you know your code is ready for production?

Hugo Häggmark

Thursday, February 17, 2011 9:04:23 PM UTC

while these are good questions..... they all stem from very similar schools of thought. Very "Uncle Bob" like questions. They are very "pop" soft dev stuff. So if you are a fashionable geek, you'll have no problem with this stuff.

But my problem is, you can know all this stuff and still suck at writing software.

In fact it can make you suck even more at writing software...... implementing massive n'tiered, pattern bloated, acronym compliant, software. Adding 1 tiny thing can ripple through lots of layers of software and it becomes *slow* to do anything. TDD tests that just test layers and layers of CRUFT. Kool Aid frameworks. Hopeless.

Keith

Thursday, February 17, 2011 9:06:19 PM UTC

It seems like some people are upset that these questions are too "vague", and don't have enough technical detail. I think that these people are missing the point. These should not be asked *instead* of specific technical questions or coding checks, but rather in addition to.

I have a very different expectation of a "senior" or "lead" developer than I do of an entry-level one. I expect that a senior dev has an ability to interact and communicate with others. I expect that they do things in a given way for a reason, and that they are analytical and reflective enough to tell me why. Open-ended questions with no clean-cut correct answer are perfect for evaluating these things.

Furthermore, conceptual questions about practices and trends help to reveal where a person's motivation comes from. Are they learning in response to the immediate needs of their day to day work? Or are they going beyond that and investing in themselves by stepping outside their comfort zone and immediate environment? Are they hidden away heads-down in a corner grinding alone on all their challenges, or are engaging with the community to find new and better ways of doing things?

I expect a senior dev to do more than just sit there and write code. I expect them to think, reflect, be aware, communicate, and invest in themselves. Candidates for such positions should absolutely be asked questions that foster a conversation where they can illustrate those skills and values, or fail to do so, as the case may be.

www.turbulentintellect.com

Thursday, February 17, 2011 9:07:10 PM UTC

- What processes should every project have in place?
- What value do daily builds, automated testing, and peer reviews add to a project? What disadvantages are there?
- How can you mitigate technical debt?

Jeff Yates

Thursday, February 17, 2011 9:07:23 PM UTC

@Bobby Cannon Thanks. I agree, my examples were not especially challenging as code. But my philosophy is, they don't need to be. You can tell most of what you need to know about the candidate from how she talks about fairly mundane code. Does she struggle to find any flaws at all without the aid of a debugger or an IDE plugin? How does she express her opinions? Does she understand more than one point of view--is she at least aware that reasonable people disagree about, say, early exits from functions? Does she have a sense of various schools of thought--say, mockist vs classical tests, or functional vs OO idioms, or declarative vs imperative style? Is she likely to be able to propagate her knowledge to junior devs? Will she be able to articulate her opinions in a team code review or architectural discussion? Does she listen to your suggestions? Will you enjoy collaborating with her? Does she seem committed to team development? If you mention something she hasn't encountered, is she curious about the new idea? Is she conscientious, disciplined, and systematic, or will she make a mess for someone else to clean? Is she creative but able to work within team contraints? Is she a relentless problem solver? I'd weigh any ONE of these factors more heavily than her knowledge of any given pattern, tool, or even dev stack. The laundry list of facts is just a starting point for assessing the knowledge worker you're going to choose as a colleague. I want a glimpse of the candidate's mind, not a vocabulary test.

Mark Knell

Thursday, February 17, 2011 9:11:44 PM UTC

It seems there are a fair number of people asking for answers to these questions. What about setting up a wiki where we can post these questions along with brief answers and links to more reading. Personally, I feel I did quite well with these questions, but it would be nice to "check the answer sheet" and make sure I'm not off base. If enough people are willing to contribute answers, I'll set it up.

Thursday, February 17, 2011 9:16:49 PM UTC

I'm only a couple of months out of university and I immediately knew the answers to all but a couple of those questions. I'm a design geek and I wish junior dev interviews were that straight-forward. I find this high-level stuff much simpler to grok than the nitty-gritty technical details we get asked in junior dev technical assessments.

Martin Doms

Thursday, February 17, 2011 9:19:56 PM UTC

@ Jeff Yates

"- Left to your own devices, what would you create?"

Now THAT is a hard question. That's a cert for mind-blank syndrome.

Andy

Thursday, February 17, 2011 9:20:33 PM UTC

I always like to ask candidates about their favorite dev tools. NOT just the ones they've used, but the ones that they really like on a gut level. And after they've gushed over some features, I ask them to tell me what, if anything, they dislike or would change about those tools.

If a person can't tell me why they like a certain tool, then I don't think they have much experience using a wide variety of tools. If they can't tell me what they dislike about a certain tool, then I don't think they've really spent enough time using it.

Kelly

Thursday, February 17, 2011 9:28:22 PM UTC

I find job postings and interview questions fascinating in what the say about people on both sides of the table. Here (and commonly), the use of the term "Engineer" is used differently than it would be in, say, the mechanical or avionics fields where engineering is identified mainly by contrast with science. Engineers take science (and philosophy) and apply it to make things with positive net benefit to society, if you believe in the creed. So I suppose I tend to focus more on what a person can create rather than what they can describe. Maybe something like:

"Let's talk about trade-offs. Tell me about some of the components you like to use, and how the fit into a couple systems you've help build." And then try to understand if the person thinks or merely acts.

Lee

Thursday, February 17, 2011 9:50:05 PM UTC

I don't put to much stock in these sorts of questions. Our industry doesn't have much of a standardization in vernacular and many of the concepts asked above are new or transient in nature. I think the best interview of person is to sit them down in front of an IDE and give them a small programming project. Tell them to pretend they are writing for a production environment (rather than hacking away) and see what they do. Do they define some interfaces? Write tests? Use inheritance? Is the code readable? Do they take into account threading issues?

After they are done ask them to modify the program to meet a new requirement. Watch what they do. When they are done, ask them why they made certain decisions.

The number of candidates I've had come through the door that can talk the talk but fall to pieces when put in front of the IDE is amazing. I'd much rather have a person work for that knows the principles of SOLID but not acronym than a person that knows what the acronym stands for but can't apply the principles.

Matthew Schumaker

Thursday, February 17, 2011 9:57:40 PM UTC

I agree with David Brabant.
"Show me a portfolio of all the applications you worked on, and tell me how you contributed to design them. Isn't it the only question that really matters?"

I think that these class room questions do not help you find a problem solver. Many are really silly.
Does knowing about an anti-pattern really show you anything? Understanding why patterns are important is a good question because it is pertinent to development today. Who really cares what a YAGI is? Don't we have dozens of terms out there that we can throw at a developer to trip him up? What does this get you?
This seems to be a measuring contest. Can I prove that I have more trivial knowledge than you?
Ive coded in .NET since Beta1. Ive developed in other languages and on other platforms as well. Ive never failed on a single project no matter what tool I used and I make sure that I have a complete understanding of the architecture I am using even if I do not remember your terminology. I follow best practices and also know of best practices because of my years of experience. Most of this type of questioning produces nothing but an academic. We want experts right? People who know and love technology. I wonder if we gave a good doctor a pop quiz, would he pass the test. Sorry doctor Oz. There must be a better way.
Furthermore, one thing is for sure, after 15 years in this industry I will not take a written test, so before you call someone in for an interview, let him know if you are planning to pull out an exam.

nate

Thursday, February 17, 2011 10:01:13 PM UTC

Q1: What is the difference between interfaces and abstract classes and when to use these?
Q2: Explain how publisher/Subscriber pattern function and how to use it to eliminate problems reconnecting clients to servers

Hussam Ahmad

Thursday, February 17, 2011 10:13:37 PM UTC

1)what blogs do you read
2)When is logging to much logging
3)why use AOp for logging
4)When to use property injection over constructor injection
5)When would you not use an ORM
6)what other uses can you think of for AOP
7)What is a T4 template
8)write some lamdba expression in VB.Net
9)Why F#
10)Should you use a designer to make your view or not, what are the disadvantages of using a designer
11)Have you ever read a blog of the famous chrissie1
12)Do you want a chocolate?

Done.

chrissie1

Thursday, February 17, 2011 10:18:23 PM UTC

I'm still just a web dev, but here are a couple of questions that I use as barometers of current knowledge

- What's the difference between a web farm and a web garden, and what are the differences in preparing a website for deployment to each of them.
- If you're starting a greenfield web project, what third-party libraries do you include in your lib directory and why? What do you add to web.config by default?

Thursday, February 17, 2011 10:23:01 PM UTC

Looks like a b tag has been left open since Nate's post!

Andy

Thursday, February 17, 2011 10:29:50 PM UTC

"The" Factory Pattern? My GoF book has two...

Jim Cooper

Thursday, February 17, 2011 10:31:27 PM UTC

I think these are wonderful questions, but what is important is that the candidate should be judged based on thought process more than whether they are right or wrong. It is the application of these principles etc that is more important that knowing the theory behind them all.

Heres one question that I would ask :

Given the Quad - Time, Cost, Client satisfaction and Best Practices, how will you prioritise them for a project you are working on? Explain why?

Pramod Raghavendran

Thursday, February 17, 2011 10:35:17 PM UTC

Good question Pramod.

I imagine in a real life environment, Cost will always be #1 priority. I'd have client satisfaction as #2, and then i'd have the other 2 as #3 and #4 but the order they appear would be open to debate.

Andy

Thursday, February 17, 2011 10:36:24 PM UTC

Hi Scott,

Greate questions / subjects. But I miss something about the DRY principle....
So : "What does DRY mean and why is it important?

Jaap

Thursday, February 17, 2011 10:41:16 PM UTC

I'm not sure I would be satisfied with my own answers to these questions. Many of them seem like good topics for blog posts just to explore my own understanding and clarify to myself how I might answer them.

Tyler Jensen

Thursday, February 17, 2011 10:47:18 PM UTC

One I've asked for many years now is:

You have two computers, and you want to get data from one to the other. How could you do it?

Generally people will come up withe one, or maybe to solutions, to which I answer, "and what else?". I keep asking for more solutions until they run dry.

The idea behind it is to test how they question requirements, and also how inventive they can be. There is no right or wrong answer, but it can give you a good idea about how easily someone might get "stuck" on a particular solution, and how much of a self-starter they might be.

Phil

Phil Kan

Thursday, February 17, 2011 11:10:34 PM UTC

@Phil

I've used that same technique myself. I learned it from a former boss who used it in my own interview. I guess I did OK.

I like to throw in questions about durability. For example, in an RPC scenario, what would happen if the response is lost? How do you avoid duplication?

I also like to add the requirement that only one machine gets to work on a particular item. How do you ensure that someone else isn't working on it. I'm continually surprised by how many answers there are to this one, each with its own set of problems.

Michael L Perry

Thursday, February 17, 2011 11:19:45 PM UTC

What would you do if you were in charge of a team of people who refused to change and were set on doing things the wrong or outdated way?

How would you handle a team member who took code reviews personally or would refuse to make the suggested changes?

DotNet Dude

Thursday, February 17, 2011 11:27:20 PM UTC

I say - what you YOU ask YOUR INTERVIEWER -
http://blog.wekeroad.com/thoughts/how-many-columns-does-an-int-have

Rob Conery

Thursday, February 17, 2011 11:56:38 PM UTC

What is DDD ? Why is it important ?
What are aggregate roots ?
What is ServiceBus ? CQRS ?
Difference between unit test and integration test ?
How you know your design is good ?
What means that a class is immutable ? Make one ? Why is it important ?
Difference between scale-out vs. scale-up ?
How connection pool works ?
What is SQL injection ?
What is an ORM ?
Would you use DataSets ? For what ?
What is memchached/AppFabric Caching ?

Petar Repac

Friday, February 18, 2011 2:25:45 AM UTC

In my experience any question beginning with "What is.." or "Describe.." is too easy for a candidate to BS their way through by Wikipedia-ing during a telephone interview, or just having learnt parrot-fashion with no real understanding. You might get a satisfactory answer, only to put them in front of a PC on their first day on the job and they'll have no idea when to use that buzzword they memorized.

I like turning the questions around into scenarios so you can test peoples problem solving abilities, for example:

1) What are a few good practices to follow (and avoid) to make your code testable?
2) How would you communicate between a Website and a Windows Service?
3) If your database was under a lot of strain, what are the first few things you might consider to speed it up?
4) How can you stop your DBA from making off with a list of your users’ passwords?
5) What do you do when you get stuck with a problem you can't solve?

Andrew Murray

Friday, February 18, 2011 3:03:07 AM UTC

These are some great questions overall, really like most of them. That said, what about coding questions? I've seen people that could answer every one of these, but if I asked them to remove the duplicates from a list, they'd be clueless. I call these people "non-coding architects" and they're surprisingly common and often have 15+ years of experience and many applications shipped on their resume.

I don't care how much you know, if you can't write code you suck. If you can write code but you don't know the fundamentals of Computer Science (data structures and algorithms mostly), you still suck. I can implement a linked-list on a whiteboard in less than two minutes (coming to alt.net seattle? Time me. I'm serious), I would expect ANYONE that I would want to hire to be able to implement some sort of linked list class in <15 minutes. Knowing concepts will only take you so far (believe me, I'm a professor, I know this well) but being able to know + do is what counts.

Jeff Jeff

Friday, February 18, 2011 3:26:34 AM UTC

I had just switched over to ASP.NET MVC in the past year from several years of ColdFusion. While I knew I still had lots to learn, I was feeling like I was starting to really get it...

Then I read this post and realized I have a really long way to go :)

Of course, that is why I am having so much fun.

Friday, February 18, 2011 3:34:01 AM UTC

Should I be concerned? Most of the questions here are not ones I could answer with a high level of confidence, and they are for a title I currently hold.

I'm in the "learn how they think" camp. I want to find people who are passionate about building software. I'm more interested in learning a person's aptitude than in testing their discrete skills. Anyone who knows how to think and solve problems can search, find and learn what they need to execute a solution in any given problem domain. But more importantly, basing qualification on skill is subject to rot. Is the technology they are quizzed on going to be applicable in 5 years, 2 years, 6 months? Whether they can regurgitate an acronym now won't help then. They need to be able to adapt and grow.

Unfortunately it's far more difficult to gauge aptitude than to quiz on concepts or code. That's why I prefer to just converse. Certain questions are good catalysts for conversation, usually those involving projects about which the candidate can speak knowledgeably and passionately. If they can't do both, you find yourself digging for more questions, or that old "what's wrong with this code" test and it's easy to question their qualification. If they can, you regret having to pass them on to the next interviewer. That's the candidate you want to hire. After they've filled out the HR paperwork they can learn SOLID, MVVM and IoC (if they haven't already started to on their own).

Peter Lanoie

Friday, February 18, 2011 3:51:05 AM UTC

Many of the questions are focused on the acronym-of-the-day.

Maybe these are the kind of interview questions companies are asking but I have to disagree that they (or answers to them) convey a candidate's proficiency as a developer or their seniority. IMO, the "senior" prefix should signify that a developer has a significant amount of experience although I all too often see it applied to one-company-one-product-three-years-work-experience kind of people.

Much of the "fashion of the day" terminology rarely make it "down to the floor". (Well, maybe it does at Microsoft but then you're different than the rest of the industry in a whole lot of ways; a lot larger, a lot more resources/manpower behind every line of code, muchlonger product cycles, etc)

Some of the "fashion of the day" terminology stuff is a way to formalize and convey the "best practices" and "common sense" that one normally picks up over the years into a more digestable [documented/discussed in blogs and conferences] format for the juniordevelopers.

I'd suggest posing a couple of real world problems and asking for a candidate's approach to solving them would be a better way to distinguish between a [good] senior developer and the rest of the crowd. That, and past track record in delivering real world apps that are usedand liked by the users... :)

Just my 2 baht...

KristoferA

Friday, February 18, 2011 4:12:10 AM UTC

I know _exactly_ the question I would ask a person wanting to work for me as a senior .Net developer: "What's so great about PHP?" Seriously, what would you say? Would you hedge, fearing to be too complimentary? Would you bash it? On the sincere side, what qualities would you pull out as admirable and worth emulation?

The same ploy works for any "antithesis" technology, process or even personality. Interviewing for an Agile team? Ask "A lot of really great software was developed under the waterfall process, why and how did that work?"

Lee

Friday, February 18, 2011 4:18:37 AM UTC

+1 to all three of: Peter Lanoie, nate, and Matthew Schumaker. Spot on.

KristoferA

Friday, February 18, 2011 4:20:07 AM UTC

These are questions I've seen asked and have asked others myself, which I think help get to a person's ability to communicate and self-develop:

1. Describe the structure and contents of a design document, or a set of design documents, for a multi-tired web application. (Points if the person mentions the typical layers of an app. Bigger points for mentions of sequence and class diagrams. Even bigger points if he/she mentions writing docs for support/operations groups.)

2. Describe a software development life cycle that you've managed. (Points if the person actually has participated in one. Bigger points if it involved source control and reviews.)

3. How do you react to people criticizing your code/documents? (A senior person should be thanking others with genuine gratitude for their input when he/she is wrong or for a good idea, and be able to defend his/her thinking in a constructive manner.)

4. Whose blogs or podcasts do you follow? (Points if the person mentions some. Big points if the person blogs. Out of the dozens of devs I've known and worked with, only 1 didn't answer "none", and he's fantastic. This is one of the blogs he mentioned :)

5. Tell me about some of your hobby projects that you've written in your off time. (Points if the person has hobby projects. Big points if the person's face lights up and he/she goes deep into design details and issues encountered.)

6. Give the person a little coding exercise with somewhat incomplete or slightly vague requirements. If they write the whole thing without asking questions, bad. If they write a bit, then ask some questions, good. If they ask a bunch of questions to clarify what's up to them vs. what's absolutely required before writing any code, outstanding. In all cases they need to explain the decisions they made. It just needs to compile on paper, though.

James McLachlan

Friday, February 18, 2011 4:21:41 AM UTC

IMO, the questions with the most votes in each category on StackOverflow.com are also helpful from an interview point of view.

Anil

Friday, February 18, 2011 4:44:59 AM UTC

I would also add:

Do you watch channel 9
Name the 3 Scott's
Are you a Mac or PC (I will pick a Mac guy for Windows and visa versa)

Mouhammad Fakhoury

Friday, February 18, 2011 5:09:50 AM UTC

I didn't have time to read through every single comment, but I found some good responses and James McLachlan more or less summed up my thoughts as well.

I don't give a rat's ass about SOLID or YAGI or any of these other buzzword bingo terms. I don't care what TDD or BDD or even DDD is. I need to know that you actually have practiced the craft of coding, software engineering, programming, software architectural design, whatever you want to call what it is you do. I want to give you a small, quick, yet challenging interactive test to see if you truly understand algorithms and implementation details concerning them. Can you work within the limitations or constraints of an existing system? Can you impose restrictions on yourself in order to improve your productivity and possibly others' too?

Communication is probably the most important skill you need. Can you communicate with me and other team members precisely and succinctly? This is very difficult to do, and most of the problems faced at a software development shop are centered around poor communication. I need to see moderate to excellent skill level in written and oral communication. I don't care about ERDs or UMLs or flow charts or any of that nonsense. Write it in plain English, clearly, precisely, and unambiguously, because it won't get any clearer with your drawings that gloss over key details of the system and/or design.

I also need someone who is more action oriented than discussion oriented. Smart people don't waste their time endlessly listening to themselves and others babble on and on. If you could have implemented a proof of concept in the time it took you to gather everyone up to discuss the potential solution, you just wasted everyone's time. Something to look at and work with is far more descriptive and useful than abstract concepts discussed at length.

These are the types of things you find out about the interviewee long after the interview process is over, and it's a lot harder to fire someone than it is to hire someone these days. I like to get it right the first time.

James Dunne

Friday, February 18, 2011 5:26:37 AM UTC

I like to start off interviews by saying, "The questions I'm asking are much more important than anything you have to say."

Then I speed-question using trivia-type questions and never, under any circumstance, allow the person time to answer properly. I find that this let's the other person know that I am not an interviewer to be toyed with.

Tim jf

Friday, February 18, 2011 6:24:38 AM UTC

I would add:
- Explain Command-query separation
- What Source Control systems have you worked with
- What is Continuous Integration? Have you used it and why is it important
- Some questions about basic data structures and algorithms (Lists, Linked Lists, Trees, Sorting etc.) and a basic discussion on the trade-offs between choosing different algorithms/data structures

Carel Lotz

Friday, February 18, 2011 7:51:22 AM UTC

Next time around I have to interview a senior dev, I'll make sure we have access to a whiteboard. Then I'll come up with a case to which I'd like to see a diagram of the technical design.
Also I'll present a similar diagram of one of our applications and ask questions about how and where to add certain functionallity.

To me, these are the most important points for a senior dev in order to add value to our team. If you can't do this, you are not hired.
Then I'll ask some questions about technology they have worked with that require more underlying knowledge. I find this is important to test someones curiousity to how things work and their ability to find out about it.

Jonathan van de Veen

Friday, February 18, 2011 7:53:53 AM UTC

Hi guys,
I come from Germany and wiork as a ScrumMaster. I would like to present my point of view. Most of the suggested questions would either make me leave during an interview or have me internally decide to not work for the company.
I totally agree with David, who suggested to have the applicant present a list of projects he has worked on and then talk about that. I don't want to and I don't need to pass a "Test" of knowledge questions to be able to work for somebody. Any HR person will tell you, that it is important to have a certain knowledge (which will be presented by certificates and credentials). More important are the "Soft Skills".

And it is not like the applicant is the only person who "wants" something during an application process (and therefore has to pass multiple tests). The company wants the applicant as well...or to be more precise...his contribution to the enterprise. And it is, in my opinion, no value contribution at all to be able to explain who the "gang of four" is. So I would focus my questions on "how" can this person contribute to my company. Is he stress-resistant, a teamplayer, does he have a good capability of self-organization, can he explain things to other team-members, etc.

And in my opinion, the list of projects and WHAT the person contributed to these projects is a good way to explore these facts. To be able to explain the difference between TDD and FDD is not...in my opinion.

Marcel Konnegen

Friday, February 18, 2011 8:24:43 AM UTC

Hi,
Yes these questions are very important and I have come accross them many times. I think every developer knows they are important. the Questions is, what are the answers? :-)

Kourosh Saleh

Friday, February 18, 2011 9:19:45 AM UTC

@Hugoware and @Marcel

The purpose of "Gang of Four" question IMHO is to detect if you ever did any research, learning or work related to design patterns, because that is something that Software Architect do. And if you ever did, you definitely had to know about the book written by four guys (hence the "Gang of Four"):

"Design Patterns: Elements of Reusable Object-Oriented Software"
http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612

(affiliate code free link)

This book is mentioned in almost every book I read about the software design and architecture.

Friday, February 18, 2011 9:25:37 AM UTC

So tell me about a project you've worked on that hasn't gone very well?

Richard Astbury

Friday, February 18, 2011 9:35:24 AM UTC

These questions are interesting, but I like the idea of a question like "How would you go about writing code to read and write INI files, without using the specific Win32 API".

The advantage of this is most people are at least vaguely familiar with it, and if they aren't you can give them the gist very fast. However, INI is incredibly loose in specification. This leads to all kinds of potentially interesting discussions. For example, does the candidate spot some of the issues up front without prompting, or do they take a simple approach and announce "Done!".

How would you handle comments, especially when writing files. For example, is there a strategy that will let you delete sections and keep comments consistent? How would you handle writing to ensure that you don't get conflicts? Can you make sure if you code crashes the user is let with something usable? Should you read to memory and cache or parse the file each time? Then there's all the fun to be had with quoting, handling white space, and crazy stuff like:-

Key Name = Someone's+"value=1;" ; this is a weird one

How you cope with the different "flavours"? Line endings? Backslash quoting? Do you make everything an option?

I think just talking aloud through an algorithm to parse the lines and handle quoting and spaces would reveal a lot about someone ability to model code in their head and test it in their head.

Perhaps these are more for a coder than an Senior Software Engineer, but I'd still like a Senior Engineer who can code, or at least reason about code.

John Carlyle-Clarke

Friday, February 18, 2011 9:42:14 AM UTC

Nothing about requirements and nothing about software processes?

Anthony Finkelstein

Friday, February 18, 2011 9:57:03 AM UTC

Though I wouldn't be surprised to be asked a lot of the questions. They are not the kind of questions I like to ask candidates when I interview. All the above questions is something you can google and memorize. I wish to see people think. I wanna know how they solve a problem. Sure if they can name and explain a few patterns* at least they have studied (for the interview).
I usually describe a system such as a fancy water boiler and ask the candidates to model it if they were to implement the software for it based on the design I ask them a lot of whys and coulds. "Why does those classes derive from the same base?" "Could you decrease the coupling with a gain and if so what would the gain be"

If I was to add anything to the list of googlable questions it would be:
Describe the liskov substitutional principle and describe when and why it's important. If the candidate does not know the principle I'll explain it and ask the latter part of the question again

*as an aside most descriptions in GoF fails to be patterns in the pattern language sense, which at least one of the authors admit

rune funch

Friday, February 18, 2011 9:59:56 AM UTC

My concern with technical interviews is that, quite often, they tend to over emphasize what the interviewer knows, compared to what the interviewee knows. Inconsciously (or at least I hope this is unconscious) this turns to an ego fight. "See how much more I know than you do". Or at least, "In my context I'm more buzzword compliant than you are."

At that game, the interviewee always loses. Because we live in a world where learning is essentially driven by context. Your personnal "technical history" leads you to what you know today. You cannot know everything. What is important is how good you are at learning and understanding complex things. Questions in a technical interview should focus on these aspects, and these aspects only.

David Brabant

Friday, February 18, 2011 10:56:58 AM UTC

I like to add :
- What is Refactoring ? Have you used it and why is it important ?
- Which design/architecture patterns do you know that embed in .net framework ?

Vahid Aleheidar

Friday, February 18, 2011 11:12:17 AM UTC

It is shocking that I just did a quick Find on this page to see what had been said about "refactoring", and the word had not yet been used.

So:

Q: What is refactoring? How do you do it? Name three common refactorings.

Mark Rendle

Friday, February 18, 2011 11:14:24 AM UTC

And somebody had finally mentioned it between me loading the page and posting my comment.

Vahid, I salute you. O>

Mark Rendle

Friday, February 18, 2011 11:17:13 AM UTC

I've been quite amused by the following typo : "a multi-tired web application". It's probably a very tired web application that's been working 24/24, 365/365 for quite some time now..

Andrei Rinea

Friday, February 18, 2011 11:53:25 AM UTC

One I've used a lot this year:

"When you have to decide for a bug or feature whether to re-write a chunk of code or keep an existing sub-optimal implementation, how do you approach the problem and communicate with your colleagues and managers?"

Friday, February 18, 2011 1:08:07 PM UTC

Well, I disagree with the idea "I don't care about design patterns or buzzy words".
Let's say that in an job interview you ask to the candidate:
--If we where designing a framework with fluent interfaces, how you would model this scenario.....?
or
--Can you write some code to walk thru an AST using the visitior pattern?
If the candidate doesn't known the patterns or the buzzy words, it'll take you a lot of time
to explain what is your point or what you are asking for, other wise your chat would be more "Fluent" ;-)
Even though I think that buzzy words and design patterns are important,
when it comes to job interviews, I always stand for the phrase,
"Talk is cheap, show me the code"

amiralles

Friday, February 18, 2011 1:14:39 PM UTC

I agree with a few posters on having to be careful about question lists like this. I only use Interview Questions lists like this when I'm looking for a job myself. The reason being is I know there are interviewers out there that ask questions like this, so I memorize a lot of answers and then never use a high proportion of the answers ever again in real life work. Also, I wouldn't consider asking 2 different candidates the same questions. It just doesn't work. I remember an interview I performed a long time back where a recruiter was telling me all their interview questions the day before. That's something you might want to think about!

Now, don't get me wrong, there are a few gems in there that are similar to interview questions I ask myself. But they are all primers that lead me on to the real questions which tell me "how they think" as opposed to "what they know".

Conor Gallagher

Friday, February 18, 2011 1:21:50 PM UTC

Actually, after re-reading your blog post I realised you're compiling a list of possible interview questions for a friend as opposed to a complete list you may use yourself!

Here's one I was asked recently:

Tell me about the most cost effective application you've ever written? What was it written in? Why was it the most cost effecitve?

Conor Gallagher

Friday, February 18, 2011 1:38:47 PM UTC

Amazing collection of question, though I don't know the answer to most of these. I spent an hour of reading it and the valuable comments on the same and that one hour was the most learned hour of my engineering graph :)
Thanks everyone...

Sagar Mody

Friday, February 18, 2011 1:51:43 PM UTC

The YAGNI concept is an important one - don't neglect it (or misspell) ;)

Saul

Friday, February 18, 2011 2:07:53 PM UTC

Tim jf ... are you serious? The point of an interview is to find a person to fill the job and be good at it....not to make you, the interviewer, feel like a big guy. If your not interested in what the interviewee has to say why are you interviewing him/her in the first place?

Seriously, if you did that to me I would probably cut the interview short, thank you for your time and walk out. Remember the interview process (especially for senior developers) is a two way process!

Paul Stanley

Friday, February 18, 2011 2:26:35 PM UTC

The one question that stands out for me is this. In an interview I was asked what three questions would I ask to see if someone knew <insert subject matter>.

Darren Jackson

Friday, February 18, 2011 3:39:52 PM UTC

Describe, in as much detail as you think is relevant, what happens when I type "google.com" into a browser and press "Go".

It's amazing how many people working on the web don't understand fundamental details such as request/response or the handoffs between IIS and the application server. I use this question as the entry point into more specific questions, many of which are represented here already.

Seth Petry-Johnson

Friday, February 18, 2011 4:34:37 PM UTC

I think between the initial post and all the follow-up comments, there's a great diversity of general concepts (good since it applies beyond .Net) and specific concepts/acronyms (good since it enforces that you're keeping current on development trends).

I think it would be a great exercise to type out my own responses in my blog, just to see where I'm at. I already saw a handful of them I don't know, and it gives a springboard for what I need to learn next! I guess I'm not as "senior" as I think I'm getting as a developer. 8^D

Dillie-O

Friday, February 18, 2011 4:58:07 PM UTC

While I agree with a lot of the more general questions, if someone asked me all those questions at an interview, I would likely not want to work for them. I once had someone ask me the proper c++ syntax for declaring an abstract function. I have used abstract functions several times and was able to explain what they were, but he basically wanted to rail me on technicalities like adding "= 0". These sorts of things can be looked up when needed. The guy proceeded to mention that they really wanted to hire someone who really knew their stuff (read the same book more than once) and did not want someone who needed to use a google search to look things up. Needless to say, I left there thinking that I would not work there if my life depended on it... I feel sorry for whoever ended up working for the guy.

Instead of quizzing someone to death, it is better to talk about previous projects they have worked on in the past. Communication is everything in this field, and if they don't have good communication skills, none of these questions will matter. You can always read up on the latest design patterns, etc, at the time you need them.

Dan

Friday, February 18, 2011 4:58:14 PM UTC

In my opinion this interview questions are irrelevant and won't find you good developer. They will find someone who is very into theory and maybe make interviewer feel "big" in candidate's eyes. Even that I can answer for most of them easily, if someone would ask me this type of questions on interview, I would probably not accept job offer if I was given one.

It reminded me one of interview - 1h15min over phone, from which good 50 minutes was about internal ins and outs of .net garbage collector, including questions like "why haven't you used reflector and other low level debugging tools to inspect what it does exactly". And that was "very important" even that it was all about Silverlight app where you have no influence over how it works anyway ;)

Sebastian Pienio

Friday, February 18, 2011 6:07:04 PM UTC

Don't know if it has been listed before, but I had the chance to ask a few times the question ....
-> Why does the CLR implementation propose both value types and reference types? Why not just one kind of type?
... I notice that the answer gives a good evaluation of the .NET programmer level. (Ex C++ programmers get a solid advantage here, anyway, ex C++ programmers usually becomes excellent .NET programmers).

@Kelly: totally agre with you concerning tooling oriented question, but on this particular topic I am biaised :)

Patrick Smacchia

Friday, February 18, 2011 6:37:14 PM UTC

Yeah I don't know ANY of the answers to these questions...but I've been a highly paid (mostly web) developer for a decade. Go figure! I guess there is still hope - the cushy jobs are out there. :)

Danno

Friday, February 18, 2011 7:18:21 PM UTC

Two of my favorites are:

1) What is the difference between "Set" logic, and "procedural" logic. When would you use each one and why?
In terms of SQL, I often see procedural logic within stored procedures. This then goes down the path of: "Do good developers have to know SQL?", which is not important as SQL is a language. If I said: "Do good developers have to know C#?", it would be a ridiculous statement, yet I hear it all the time with SQL. There is a vast difference between them, and now with LINQ, the difference is becoming even more relevant and apparent.

2) In detail, please describe how a client’s browser communicates with a web server.
What I’m looking for here is the understanding of how the web actually works in terms of sockets. I feel this is important because, as a professional developer, this underlying knowledge bubbles up as to why host headers are required (for example), or why duplex communications is more resource intensive.

Richard Reukema

Friday, February 18, 2011 7:36:03 PM UTC

This is a bit self-serving (Scott, feel free to moderate out), but if you think you know the answers to a lot of the questions posed here, I am currently looking to hire a Sr. .Net Developer. Send cover letter, resume, and desired compensation to me at michael _dot_ teper _at_ elanex _dot_ com. Please put GS106-SH in the email title. Thanks! :)

Michael Teper

Friday, February 18, 2011 9:31:24 PM UTC

I've noticed a lot of people have stated that these questions aren't good because they're trendy or they cover topics you don't know.

I've interviewed with Microsoft before, and I got several questions I didn't know the answer to. Those were the questions that actually sparked discussion and were also the answers I was complimented on. For example, one question was about how I would approach designing an algorithm to efficiently sort a specific type of data. In all honesty, I had no idea how to answer the question, but I also recognized that the situation was unlikely to come up in the type of web apps I would likely be working on. I told the interviewer I didn't have a good answer to the question as asked, but I laid out an analogous situation I had solved in a web environment and explained how I solved it. Rather than giving a textbook/wikipedia answer, I had a real discussion about how I approach optimization in a context that was more relevant to the specific position I was applying for.

Ian

Saturday, February 19, 2011 2:11:34 AM UTC

How do you approach mentoring/sharing knowledge with your team.

Christopher Isaacs

Saturday, February 19, 2011 3:41:29 AM UTC

@Paul Stanley To answer your first question: no. The rest of your post has been duly noted and forwarded to all known associates so they stop what they are doing immediately.

</snark>

Tim jf

Saturday, February 19, 2011 4:24:38 AM UTC

What do you read to keep up with the industry?
Explain the differences between procedural, object oriented, and functional programming.
If you are asked to implement something using a particular technology that you are not familiar with, what do you do first?
Describe the circumstances that could lead two threads to deadlock.
And of course there is the infamous fizzbuzz problem.

Nick

Saturday, February 19, 2011 11:40:13 PM UTC

"Would you call yourself a craftsman (craftsperson) and what does that word mean to you?" is a dumb question to ask. Just because they wouldn't think of themselves in those terms doesn't necessarily mean that you wouldn't think of them. That's a very particular, almost dialectical language use. It would also be grossly prejudicial against candidates for whom English was not their mother tongue.

Why do you ask them about YAGNI twice? Are you hoping to embarrass them when they still don't know what the acronym is the second time around.

David Heffernan

Sunday, February 20, 2011 2:37:48 AM UTC

Its better than asking about DRY twice.

Nick

Sunday, February 20, 2011 1:51:05 PM UTC

Is just me or are this interview question list always very web-development-heavy? Many questions are also ambiguous (is the sandbox question referring to execution-context-sandboxes or SCM-working-directory-sandboxes?).

I'd also run away from those "Name three" type of questions. A job interview is not a game show. You want to know if a candidate understands important concepts not if she memorized all "important" terms. I was always bad at this type of questions in college. I made up with that by explaining my take on the domain, why it is important and how it differs from others. That usually got me enough points without any memorizing.

Eric

Sunday, February 20, 2011 5:47:32 PM UTC

The "big picture" here is this person is going to be leading your team. After all the technical questions are over (assuming he knows his chops), what do you really know about the person? That's why it's important to move pass code and find out what this person is really about. So ask:

What do you do for fun outside of work?

I'll speak for myself here, but I'm looking for two things. The first is that he codes for fun. For me this goes without saying because if you're passionate about your craft, you live and breathe it. Finally, and most importantly, I'm looking to see that this person has genuine and deeply personal activities that anchor his spirit. If he's into poetry, I want to hear about it. If he's into community gardens, I want to talk about his last project. Into running - show me!

The idea is I want to know that you have a passion or two outside of the craft. Because all of us know, sometimes we have good days and sometimes we have bad days. I want to know that my team's moral and my lead's moral is going to be steady and consistent. Not fluctuating between the success or failure of our projects. A lead needs to have a fair amount of consistency between project outcomes and so this person needs to have something anchoring him other than code.

What do you do for fun outside of work? I want to know that you have a LIFE.

TVD

Sunday, February 20, 2011 6:45:01 PM UTC

After reading all the comments, I have made some observations:

1) There isn't an agreement as to what a "senior software engineer" should know. But that is quite ok since different companies have different standards as to who should be a senior software engineer. I have been a senior software engineer in my second job and now I am in my 5th job and I don't expect be a senior software engineer in my current company for at least a couple of years from now.

2) We all believe we are competent people (I am not saying you guys aren't, I am just saying most average and below-average developers think they deserve the job that they are interviewing for and believe that they would be able to do it decently if they are hired. And what is funny is that they are correct for a large percentage of time - not every job require superstars).

2) Most people are looking for a candidate just like themselves. If the candidate knows the stuff that I know then I would probably hire them. If they don't know what I believe is important, then I probably won't hire him. It seems reasonable but the situation is quite sad if we look at the fact that what the interviewer thinks is important can vary widely from person to person.

3) There are some people who doesn't read a lot and hence not familiar with acronyms and the names of the cool technology/process/framework/design strategies even though they might have a good sense of how to deal with situation involving them. For example, such a person might be able to arrive at an abstract factory solution for a problem where it is a good fit, without ever being aware that what he did has a name and is a standard solution for them problem he solved. Such people really hate the kind of questions where the interviewer asks him - what is dependency injection, even though he might be employing it in his projects (without knowing its name).
Then there are people who are not big on previous experience but reads a lot and is aware of what is the newest thing in the technology space. They know what the different design patterns are, what TDD is, what IOC is etc even though they might never have used them in their projects or they might never be able to come up with abstract factory on their own without having read about it in some book or website. These people make up for their lack of ingenuity by reading about stuff. Those people would love the questions listed in this blog post (please note that I am not making the assumption that all the people who know the answers to the questions above are in the 2nd category, there are a lot of developers who read books and is always up-to-date on the technology space but also might have discovered abstract factory on their own)
So which of these two kind of developers are more valuable ? I don't think we would have an agreement on that. If I am in the 1st category I am more prone to think that the 1st category developers are more valuable, same is the case with the 2nd category. This goes back to my 2nd point - we are looking for ourselves in others.

4) If we know the answer to the a question from the above list, we have a tendency to think that it is a good question. If we don't know the answer, then we are are inclined to believe that the question is not really relevant to finding a good software engineer (with the following line of reasoning - I believe that I am a competent developer and if I don't know the answer to that question, hence the question is not relevant to finding a good software engineer :-))

5) A good number of interviewers wouldn't be able to answer a good number of these questions themselves if asked in an interview.

6) A good number of people who are already in the team for the position being interviewed won't be able to answer a good number of these questions.

To summarize, i don't think we have any good solution to the problem of having to choose the right interview questions. No matter what strategy we choose, we always miss some good developers and sometimes hire a BS developer.

Pradeep Chellappan

Monday, February 21, 2011 12:52:33 AM UTC

Some of these are great and some of these are not so great, even for judging a senior level engineer. There are _plenty_ of "senior" engineers my dad tells stories of that are really not senior level at all that he deals with. I can't even answer half of these (on the spot) and I've been programming for 10 years.

A few measures I can see that are good for judging a programmer are:

1) How many and what *kinds* of projects have they worked on?
2) Have they contributed to any open source project? Do they host or manage an open source project?
3) How they deal with certain problems and why they chose the way they did
4) How eager are they to learn new ways of doing things
5) Do they think everything they touch is gold? If so, goodbye!

I feel like anything I can just Google to look up is a useless question. It's not a judge of skill or character, just how well someone remembers a tidbit of information. How they *use* it, though, is not something you can Google. Case in point: "On this piece of paper, lay out an architecture for a so-and-so type of application." I don't think there's a right answer and it'll be far from optimal, but I'd be more interested in seeing how they arrive at their solution.

Einstein once said, "Why should I remember anything if I can just look it up?" Words I live by.

Kamran Ayub

Monday, February 21, 2011 8:58:39 AM UTC

If you were asked to build an application that was "scalable", what information would you need to know and how would you use this information to build and test your solution.

What is the difference between scaling up and scaling out a solution and what are the challenges or limitiations of each approach?

Jon

Monday, February 21, 2011 1:47:21 PM UTC

Pretty interesting questions and sort of sad in a way. The problem with this approach to interviewing is that programming (especially in the Microsoft "churn out a new framework by lunchtime" world) changes so quickly no one really knows it all. Or rather, when someone does master something its obsolete in a few years. So the relavance of much of this information is either domain specific (i.e. You work for a hedge fund and do lots of multi-threaded realtime work) or "time" specific.. i.e. You came into programming when ADO.Net was really big.. so your an expert in that, however you know nothing about Linq!

What I'm getting at is that in this fast changing industry its nearly impossible to become and "expert" for more than a few years. Unlike other professions like Law, Accountancy, Medicine where every year you build on your knowledge and thus your skill improves, software requires you to re-learn the same things in a slightly different way every 3 yrs!

When I studied at University there was no such thing as design patterns, TDD, BDD, Mocking etc... To be honest you would be hard pushed to find anyone who did that stuff regularly even 5-6 yrs ago. So in that climate how can you test for real seniority in the field when for most of us, anything we learnt 10 yrs ago is useless now.

The interview questions are good in some ways because they pull out the "fans". The die-hard, live, eat, breathe code type people. And if you need that because your looking for a wonder kid who can save your ass then thats fine. But there are so few of those people because most of us want a life! They dont want to spend the rest of their lives learning how to display "hello world" in another language / framework for th 10th time in their career.

I think the questions are really a reflection of how sad a career choice software development can be if you are looking for a long term profession. At the end of the day its a young persons game or a game where you will not have a life outside of it if you want to remain in it. You have to choose what u want I suppose...

albsure

Monday, February 21, 2011 2:43:37 PM UTC

What do you know about "realtime", "NoSQL", "Socket.IO" and "Nodejs"?

ferdous

Monday, February 21, 2011 2:48:21 PM UTC

1. What do you know about "realtime", "NoSQL", "Socket.IO" and "Nodejs"
2. Have you hard of "Brewer's conjecture" or "CAP theorem"? What is it?

ferdous

Monday, February 21, 2011 3:04:33 PM UTC

As long as you the interviewer are open to taking in different approaches other than your own (no you're not a God and your way is not the highway pal) for each of these topics (every developer has their preference for example on how best to decouple, etc.) then these are alright to ask...and is an excellent list to take SOME off of but you wouldn't want to ask all of these, it's just asking for too much perfection in a developer. It's when you get those interviewers who think only their way is right and thus "the interviewee fails because of it".

I think the list is legit...for a Lead position. But looks like Sr. Devs are Lead level basically at MS.

Dave

Monday, February 21, 2011 3:16:10 PM UTC

I love Mark's suggestion above of testing with code that's likely to come up at the workplace. While I might not know the specific buzzwords I'm being asked about, I can take a pretty good guess at what well- (or badly-)written code does, and how I could make it better -- regardless of what language I'm working in. If it's something like a one-line Perl program, that's one thing, but a "normal" routine, I could figure out.

Of course, with any luck, I won't have to go through any job interviews in the near future. :-)

sarekofvulcan.livejournal.com

Monday, February 21, 2011 5:32:16 PM UTC

Why is it wrong to forget to put a cover sheet on your TPS report?

David Wilde

Wednesday, February 23, 2011 7:23:21 AM UTC

Good article. "What are some alternate ways to store data other than a relational database" would really test the knowledge of somebody.

Gautam

Wednesday, February 23, 2011 5:07:47 PM UTC

What motivates you?

Mathias

Wednesday, February 23, 2011 5:16:31 PM UTC

Can you inherit a value type, and is that (yes/no) a good or bad thing?

Expain/teach me about the architecture/design of one of the systems you recently worked on. What was good/bad about it and why?

Mathias

Wednesday, February 23, 2011 5:20:36 PM UTC

What makes a software project successful?

Mathias

Wednesday, February 23, 2011 5:34:07 PM UTC

I think the point we are all missing is not getting all the questions answered correctly, but the attitude, personality, response, controlling frustration etc are important factors when working in team environment. You can be a super dude, but if you are working with 1/2 dudes then you have to slow down as well. I would have some serious doubts about a person who would ask all these questions in an interview.

Adann

Wednesday, February 23, 2011 7:09:36 PM UTC

Its a great list.

I also started a .net question series on my blog (http://ankushbhatia.wordpress.com/category/questions/) where dev shares their views on different approchs http://ankushbhatia.wordpress.com/category/questions/

Though I find really diffcult if somebody asks me a list of questions like this and expect to answer everything.

Ankush

Ankush

Wednesday, February 23, 2011 9:20:37 PM UTC

Have You tried functional programming? What are the key differences that matter to You? When Do YOu like to use functional and when object?
What is the difference between programming a website (a shop, a social network) and a high-volume processing system (a transaction processing system a risk simulation engine). Do YOu use different patterns, tools etc? What stays the same.
What's You favorite algorithm? When was the last time You applied some well-known (or perhaps not so well known) algorithm to a problem? Did You solve some puzzles lately using computer programming?

I personally the last one. I like programmers know problem solving techniques, not only frameworks and patterns. This make them also aware of something else than keep up to speed with the latest technologies and patterns (which change every 2 years apparently - something like a moore law for software development)

Łukasz Dziekan

Sunday, February 27, 2011 3:13:50 PM UTC

Must add...

Why do you want to work as a developer here? Why don't you go home and write the next *big thing* yourself? If the developer doesn't see the value in collaboration, then I think somethink is missing. I think it's also a good ego-check for 12 page CV's. ;)

John Douglas

Monday, February 28, 2011 4:24:54 AM UTC

I have found after 15+ years in this industry and reading the comments here that I am one step closer to wanting to sell painted coconuts to tourists in Cancun.

Andy Evans

Saturday, March 12, 2011 11:18:35 AM UTC

I think you've reverse-cargo-culted... Confusing the ability to recite "latest trend" definitions with the production of quality software. The lesser of your offenses is the implicit assumption that OOD is the only principle that matters, thereby sideswiping those of us that might use different paradigms to deliver quality software. I personally gave up design patterns once template support was added to C++... And have since moved on to a more Functional style of programming.

The absolute best way to interview, bar none, is to screen the applicants by having them complete a programming problem. Something not too complex, but not overly simple, so you can actually see their code (you wouldn't hire a band for a party w/o hearing them first).. Then, if they pass that test, bring them onsite for a day of whiteboarding (you can start with FizzBuzz, and work your way up to code to check if a graph is acyclic)...

Unless of course, you're mainly interested in how well someone can call an API and write a consumer facing website, in which case I guess these questions work well.

"Object-oriented programming is an exceptionally bad idea which could only have originated in California." -- Edsger Dijkstra

"I find OOP technically unsound." -- Alexander Stepanov

Sunday, March 13, 2011 5:21:12 AM UTC

I think the interview questions for this career is totally tough, as tough as its competition. You know, being a software engineer is a tough job, it requires a lot of effort and logic to cope up with the career.

interview preparation

Monday, March 14, 2011 2:39:11 PM UTC

In my opinion all this questions are relevant, because here we are stating potential questions, that a senior software engineer could encounter in an interview. Anyway I don't think there is a good question and a bad one. Even if the question has little or no value, even if the candidate doesn't know the buzzword, it is always interesting to see how they manage a response and how they react to this situation. I join many others here in that, in an interview, we should aim for knowing the candidate and I assume that that's the purpose of the candidate also. For that purpose we only have one way, discussing and arguing. we should be able to evaluate the person in front of us and figure out if things will work smoothly with him. ;)

BENSASSI MOADH

Tuesday, March 29, 2011 9:11:48 AM UTC

Thanks Scott, Two interviews this week with technical tests both ripped from this page. The interviewers believing that i should know the answers to ALL the questions asked because Hanselman says so.
So i sit here with no job, trying to memorise the answers to all these questions.

Ben Mcaskell

Wednesday, March 30, 2011 8:34:30 AM UTC

I'm really sorry to hear that, Ben. That wasn't the intent of this post and I'm sorry that the interviewers used these questions against you.

Scott Hanselman

Friday, April 01, 2011 6:43:41 AM UTC

This is one of the reasons why I removed "Senior" from my CV. Really sad industry that I've been working on since age 16. At the age of 36, I reverted back to (junior) developer with enterprise applications done and selling it on my own. We are all kids playing with technology all day and night. Try to give yourself a month break and come to interview, I will make sure you look like a puppy software developer after that with latest buzzwords... You need to work on stopping the madness not spreading it all around!

Daniel

Friday, April 15, 2011 3:39:54 AM UTC

How about "how many lines is a typical method of yours?" Follow up with "why?"

Domenic

Monday, May 16, 2011 1:55:41 PM UTC

What? I thought Gang Of Four was a cool underrated english band! Obviously, I still have to learn a lot of things. Thank you Scott for this article!

Renaud Dumont

Wednesday, May 25, 2011 12:53:40 AM UTC

I can't believe no-one has asked yet but where are the (comprehensive list and explanations of) answers at then? And because no-one seems to want to say what's the answer to x (sorry I mean foo lol) I figured I would ask! :)

SteveyTxxx

Tuesday, May 31, 2011 2:53:37 AM UTC

These questions are useless trivia for anyone working in corporate software development. Maybe slightly useful for someone who wants to work for a so-called "software company". But I've used too many products produced by said companies where everyone knew "Gang of Four" design patterns, and no one knew how to make a tool that a business user could use without calling the local IT staff every 5 minutes.

Your n-tiered application with a beautiful object graph and a large ORM layer would get you a look of "you wanna do what!?" from most corporate app dev managers out there. No one gives a flying crap about your megabytes of XML config files - they just want the business users to be happy.

Questions for corporate software devs:
- Can you gather the real requirements directly from the users, after being emailed the contradictory "requirements" by the business analyst?

- Can you code in whatever language the idiot Application Architect thinks is in style this week? Can you "fake" enough so-called "dependency injection" BS to get them off your back so you can get back to actually building apps that people use? Can you pretend to care about "Gang of Four" when you know its just what you've been doing for years anyway?

- Can you pretend to be interested in the new buzzword that your manager wants you to learn about? He just got back from a conference and is really interested in XML-RPC since its supposed to be the bee's knees!

Meh

Wednesday, June 01, 2011 5:27:51 AM UTC

trolling, trolling, I am trolling !!!

Vasile

Wednesday, June 01, 2011 5:31:16 AM UTC

Here are some answers to some of the questions

http://standupprogramming.com/2011/02/21/purely-fabricated-interview-expert-pattern/

Vasile

Wednesday, July 27, 2011 2:15:15 PM UTC

Interview questions are important. I am digging all patterns.

How do we figure out if we are interviewing with the right company? How do we interview the interviewer on their "best practices", expectations, scope, BS ratings (AAA is the poorest BS rating), team dynamics....

SamG

Sunday, September 04, 2011 11:07:11 PM UTC

Name the people in this picture, and explain why it's hilarious. (Sorry, couldn't resist :)

James McLachlan

Comments are closed.

Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.

practice interview questions

2013-10-11T02:42:00.003-07:00

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New Interview Questions for Senior Software Engineers

February 17, '11 Comments [158] Posted in Learning .NET | Programming

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Understanding session state modes in asp.net

2013-10-11T00:43:00.002-07:00

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Patrick Y. N...

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Microsoft

Understanding session state modes + FAQ

Jul 02, 2002 04:51 PM|LINK

Last updated: Sept 21, 2004
Author: Patrick Y. Ng

The article is divided into two parts:
1. "Understanding Session State Modes" - to help you to understand the difference between the three modes of session state.
2. FAQ

[hr]
1. Understanding Session State Modes
Storage locationInProc - session kept as live objects in web server (aspnet_wp.exe)

StateServer - session serialized and stored in memory in a separate process aspnet_state.exe).  State Server can run on another machine

SQLServer - session serialized and stored in SQL server

PerformanceInProc - Fastest, but the more session data, the more memory is consumed on the web server, and that can affect performance.

StateServer - When storing data of basic types (e.g. string, integer, etc), in one test environment it's 15% slower than InProc.  However, the cost of serialization/deserialization can affect performance if you're storing lots of objects.  You have to do performance testing for your own scenario.

SQLServer - When storing data of basic types (e.g. string, integer, etc), in one test environment it's 25% slower than InProc.  Same warning about serialization as in StateServer.

Performance tips for Out-of-Proc (OOP) modesIf you're using OOP modes (State Server or SQL Server), one of your major cost is the serialization/deserialization of objects in your session state.  ASP.NET performs the serialization/deserialization of certain "basic" types using an optimized internal method.  ("Basic" types include numeric types of all sizes (e.g. Int, Byte, Decimal, String, DateTime, TimeSpan, Guid, IntPtr and UIntPtr, etc)

If you have a session variable (e.g. an ArrayList object) that is not one of the "basic" types, ASP.NET will serialize/deserialize it using the BinaryFormatter, which is relatively slower.

So for performance sake it is better to store all session state data using one of the "basic" types listed above.  For example, if you want to store two things, Name and Address, in session state, you can either (a) store them using two String session variables, or (b) create a class with two String members, and store that class object in a session variable.  Performance wise, you should go with option (a).

To further understand this topic, please see the question in this FAQ: "How does (de)serialization work in SqlServer and State Server mode?"

RobustnessInProc - Session state will be lost if the worker process (aspnet_wp.exe) recycles, or if the appdomain restarts.  It's because session state is stored in the memory space of an appdomain.  The restart can be caused by the modification of certain config files such as web.config and machine.config,  or any change in the \bin directory (such as new DLL after you've recompiled the application using VS) For details, see KB324772. In v1, there is also a bug that will cause worker process to restart.  It's fixed in SP2 and in v1.1.  See KB321792.

If you're using IIS 6.0, you may want to go to IIS Manager, go to Application Pools/DefaultAppPool, and see if any of the parameters on the Recycling and Performance tabs are causing the IIS worker process (w3svc.exe) to shutdown.

StateServer - Solve the session state loss problem in InProc mode.  Allows a webfarm to store session on a central server.  Single point of failure at the State Server.

SQLServer - Similar to StateServer.  Moreover, session state data can survive a SQL server restart, and you can also take advantage of SQL server failover cluster, after you've followed instructions in KB 311209.

CaveatsInProc - It won't work in web garden mode, because in that mode multiple aspnet_wp.exe will be running on the same machine.  Switch to StateServer or SQLServer when using web garden.  Also Session_End event is supported only in InProc mode.

StateServer
- In a web farm, make sure you have the same <machineKey> in all your web servers.  See KB 313091 on how to do it.
- Also, make sure your objects are serializable.  See KB 312112 for details.
- For session state to be maintained across different web servers in the web farm, the Application Path of the website (For example \LM\W3SVC\2) in the IIS Metabase should be identical (case sensitive) in all the web servers in the web farm.  See KB 325056 for details

SQLServer
- In v1, there is a bug so that iif you specify integrated security in the connection string (e.g. "trusted_connection=true", or "integrated security=sspi"), it won't work if you also turn on impersonation in asp.net.  This problem is (wrongly) described in KB 324479.  Unfortunately, the "Description" and the "Cause" sections  in the KB are quite wrong and misleading.  But anyway, there is a QFE fix for it, and the fix will also be available when SP3 ships.  The problem is fixed in v1.1.
- Also, make sure your objects are serializable.  Otherwise, your request will hang!  See KB 312112 for details.  The SQLServer mode hanging problem was fixed in v1.1.  The QFE fix for KB 324479 also contains the fix for this problem.  The problem will be fixed in v1 SP3 too.
- For session state to be maintained across different web servers in the web farm, the Application Path of the website (For example \LM\W3SVC\2) in the IIS Metabase should be identical (case sensitive) in all the web servers in the web farm. See KB 325056 for details

Other resourceshttp://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnaspp/html/aspnetsessionstate.asp
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnbda/html/CachingArchch2.asp
http://www.411asp.net/home/tutorial/specific/web/sessions
[hr]

2. FAQ's:
Question list:Q: Session state works on some browsers, but not on others.  Why?

Q: In InProc mode, why do I lose all my session occasionally?

Q: Session states works on some web servers but not on others.

Q: Why isn't session state available?

Q: Why isn't Session_End fired?

Q: Why are my Session variables lost frequently when using InProc mode?

Q: Why does the SessionID remain the same after the Session times out or abandoned?

Q: Why does the SessionID changes in every request?

Q: What is the difference between Session.Abandon() and Session.Clear()?

Q: Is the session Timeout attribute a sliding timeout value?

Q: Can I share session state between ASP.NET and ASP pages?

Q: Can I share session state between web applications (i.e. "virtual directories" or "applications" in IIS)?

Q: What kinds of object can I store in session state?

Q: Why did my request hang after I switch to SQLServer mode?

Q: How come Response.Redirect and Server.Transfer is not working in Session_End?

Q: In Session_End, do I have a valid HttpSessionState object and HttpContext object?

Q: How do I use session state with web services?

Q: I am writing my own HttpHandler.  Why is session state not working?

Q: I am using a webfarm, and I lost session state when directed to some web servers.

Q: If using "cookieless", how can I redirect from a HTTP page to an HTTPS page?

Q: Does session state have a locking mechanism that serialize the access to state?

Q: How do I detect a session has expired and redirect it to anther page?

Q: In Session_End, I tried to do some cleanup job using SQL but it failed.  Why?

Q: I am using SQLServer mode.  Why aren't my sessions expiring?

Q: I have a frameset page which has an HTM extension, and I found out each frame it contains display a different session id on the first request.  Why?

Q: I set EnableSessionState to "ReadOnly", but in InProc mode I can still modify the session.  Why is that?

Q: I set "cookieless" to true, and now my session variables are lost after a Redirect.  Why?

Q: What are the disadvantages of setting cookieless to true?

Q: In InProc mode, I change the timeout value of a session programmatically, and that causes my Session_End to be called.  Why?

Q: In SqlServer mode, can I store my session state in a database other than tempdb?

Q: How can I avoid putting plain password for my sql connection?

Q: What SQL permissions do I need when using SqlServer mode?

Q: Can I write my own custom session state module?

Q: How does (de)serialization work in SqlServer and State Server mode?

Q: How can I secure my state server?

Q: Can I subscribe to SessionStateModule.End event using a non-global.asax handler method?

Q: Can different apps store their session state in different databases on the same SQL server?

[hr]

Q: Session state works on some browsers, but not on others.  Why?  A: Assume you aren't using cookieless, you should make sure your browsers support cookie.  Also see this KB: See http://support.microsoft.com/default.aspx?scid=kb;EN-US;q316112

Q: In Proc mode, why do I lose all my session occasionally?A: Please see the "Robustness" section in the "Understanding session state modes" section of of this article.

Q: Session states works on some web servers but not on others. A: Maybe machine name problem.
See http://support.microsoft.com/default.aspx?scid=kb;EN-US;q316112

Q: Why isn't session state available?

A:
- First, check your web.config, machine.config and your page directive to make sure you have enabled session state.
Reference:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconsessionstate.asp
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpgenref/html/cpconpage.asp

- Also, please note that session state isn't available just everywhere, anytime.  It is available only after the HttpApplication.AcquireRequestState event is called.  For example, it is NOT available in the Application_OnAuthenticateRequest handler inside global.asax.
For details, see: http://msdn.microsoft.com/library/default.asp?url=/library/enus/cpguide/html/cpconhandlingpublicevents.asp

- Lastly, make sure System.Web.SessionState.SessionStateModule is included the <httpModules> in your config files.  A common case is that SharePoint application will remove this module from their web.config files (for performance reason), and thus session state isn't available.

Q: Why isn't Session_End fired? A: This is one of the most frequently asked question. 1. Remember Session_End event is supported only in InProc mode.
2. Session_End won't be fired if you close your browser. HTTP is a stateless protocol, and the server has no way to know if your browser has closed or not. 3. Session_End will be fired only (i) after n minutes of inactivity (n = timeout value), or (ii) if someone calls Session.Abandon(). 4. For case (i) (pt. 3), Session_End will be run by a background thread, which implies:

    a. Your code in Session_End is running using the worker process account. You may have permission problem if you're accessing resource such as database.
    b. If an error happens in Session_End, it will fail silently.
5. For case (ii), please note that in order for Session_End to be fired, your session state has to exist first.  That means you have to store some data in the session state and has completed at least one request.
6. Again for case (ii), Session_End will be called only if the abandoned session is actually found. As a result, if you create and abandon a session inside the same request, because the session hasn't been saved and thus can't be found, Session_End won't be called.  This is a bug in v1 and upcoming v1.1.

Q: Why are my Session variables lost frequently when using InProc mode? A: Probably because of application recycle.
See http://support.microsoft.com/default.aspx?scid=kb;en-us;Q316148
In v1, there is also a bug that will cause worker process to restart.  It's fixed in SP2 and v1.1.  See http://support.microsoft.com/default.aspx?scid=kb;EN-US;321792

For more details about app recycling, see my other FAQ:
http://www.asp.net/Forums/ShowPost.aspx?tabindex=1&PostID=232621

Q: Why does the SessionID remain the same after the Session times out or abandoned?A:Even though the session state expires after the indicated timeout period, the session ID lasts as long as the browser session. What this implies is that the same session ID can represent multiple sessions over time where the instance of the browser remain the same.

Q: Why does the SessionID changes in every request? A: This may happen if your application has never stored anything in the session state.  In this case, a new session state (with a new ID) is created in every request, but is never saved because it contains nothing.

However, there are two exceptions to this same session ID behavior:
- If the user has used the same browser instance to request another page that uses the session state, you will get the same session ID every time.  For details, see "Why does the SessionID remain the same after the Session times out?"
- If the Session_OnStart event is used, ASP.NET will save the session state even when it is empty.

Q: What is the difference between Session.Abandon() and Session.Clear()? A:The major practical difference is that if you call Session.Abandon(), Session_End will be fired (for InProc mode), and in the next request, Session_Start will be fired. Session.Clear( ) just clears the session data without killing it.

Q: Is the session Timeout attribute a sliding timeout value? A: The session Timeout is a sliding expiration time, meaning whever your page access session state, the expiration time will be moved forward.  Please note that as long as a page has NOT disabled session state, it will access the session automatically when requested.

Q: Can I share session state between ASP.NET and ASP pages? A:  No.  But there is an MSDN article on how to work around it: http://www.msdn.microsoft.com/library/default.asp?url=/library/en-us/dnaspp/html/ConvertToASPNET.asp

There are also some 3rd party solutions:
(Disclaimer: the 3rd party solutions listed below is only for the convenience of customers, and does NOT imply any endorsement from Microsoft)http://www.consonica.com/solutions/dotnet/statestitch/index.html http://www.sessionbridge.com

Q: Can I share session state between web applications (i.e. "virtual directories" or "applications" in IIS)? A: No.  Sorry.

Q: What kinds of object can I store in session state? A: It depends on which mode you are using:
- If you are using InProc mode, objects stored in session state are actually live objects, and so you can store whatever object you have created.
- If you are using State Server or SQL Server mode, objects in the session state will be serialized and deserialized when a request is processed.  So make sure your objects are serializable and their classes must be marked as so.  If not, the session state will not be

saved successfully.  In v1, there is a bug which makes the problem happen unnoticed in  SQLServer mode and will make your request hang.  The hanging problem is fixed in v1.1.  The QFE fix for KB 324479 also contains the fix for this problem.  The problem will be fixed in v1 SP3 too.

See this KB for more info:
http://support.microsoft.com/directory/article.asp?ID=KB;EN-US;q312112

Q: Why did my request hang after I switch to SQLServer mode?A: Please read the answer for the question: "What kinds of object can I store in session state?"

Q: How come Response.Redirect and Server.Transfer is not working in Session_End?
A: Session_End is fired internally by the server, based on an internal timer.  And thus there is no HttpRequest associted when that happens. That is why Response.Redirect or Server.Transferdoes not make sense and will not work.

Q: In Session_End, do I have a valid HttpSessionState object and HttpContext object?  A: You will have the HttpSessionState object available.  Just use 'Session' to access it. For HttpContext, it is not available because this event is not associated with any request.

Q: Will my session state be saved when my page hit an error?  A: If you're using StateServer or SQLServer mode, for data integrity reason session state module will not save any changes to session state if there is an error.  To work around this, you can call Server.ClearError in your exception handler.
For InProc mode, changes are made directly to the in-memory objects and so whatever changes you've made so far will stay in the memory.  However, if it's a new session, ASP.NET will not insert your session state into the internal table, and thus your session state will NOT be saved, unless you call Server.ClearError in your exception handler.

Q: How do I use session state with web services? A: The extra trick needed is on the caller side.  You have to save and store the cookies used by the web service.  See the MSDN documentation on HttpWebClientProtocol.CookieContainer property.

However, please note if you're using proxy object to call a web service from your page, the web service and your page cannot share the same session state due to architecture limitation.

This can be done if you call your web service through redirect.

Q: I am writing my own HttpHandler.  Why is session state not working?
A: Your HttpHandler has to implement the "marker" interface IRequiresSessionState or IReadOnlySessionState in order to use session state.

Q: I am using a webfarm, and I lost session state when directed to some web servers. A: For session state to be maintained across different web servers in the web farm,the Application Path of the website (For example \LM\W3SVC\2) in the IIS Metabase should be identical (case sensitive) in all the web servers in the web farm. See KB 325056 for details.

Q: If using "cookieless", how can I redirect from a HTTP page to an HTTPS page? A: Try this:

String originalUrl = "/fxtest3/sub/foo2.aspx";
String modifiedUrl = "https://localhost" + Response.ApplyAppPathModifier(originalUrl);
Response.Redirect(modifiedUrl);

Q: Does session state have a locking mechanism that serialize the access to state?A: Session state implements a reader/writer locking mechanism:
- A page (or frame) that has session state write access (e.g. <%@ Page EnableSessionState="True" %>) will hold a writer lock on the session until the request finishes. - A page (or frame) that has session state read access (e.g. <%@ Page EnableSessionState="ReadOnly" %>) will hold a reader lock on the session until the request finishes. - Reader lock will block a writer lock; Reader lock will NOT block reader lock; Writer lock will block all reader and writer lock. - That's why if two frames both have session state write access, one frame has to wait for the other to finish first.

Q: How do I detect a session has expired and redirect it to anther page? A: It's a much requested feature, and unfortunately there is no easy way to do it right now.  We will look into in the next major version.  In the meantime, if you are using cookie, you can store a marker in your cookie so you can tell the difference between "fresh browser + new session" and "old browser + expired session".  Below is a sample code that will redirect the page to an expired page if the session has expired.

void Session_OnStart(Object sender, EventArgs e) {
    HttpContext context = HttpContext.Current;
    HttpCookieCollection cookies = context.Request.Cookies;

    if (cookies["starttime"] == null) {
        HttpCookie cookie = new HttpCookie("starttime", DateTime.Now.ToString());
        cookie.Path = "/";
        context.Response.Cookies.Add(cookie);
    }
    else {
        context.Response.Redirect("expired.aspx");
    }
}

Q: In Session_End, I tried to do some cleanup job using SQL but it failed.  Why? A: First, Session_End is supported only in InProc mode.  Second, Session_End is run using the account which runs the worker process (aspnet_wp.exe), which can be specified in machine.config.  Therefore, in your Session_End, if you connect to SQL using integrated security, it will use that worker process account credential to connect, and may fail depending on your SQL security settings.

Q: I am using SQLServer mode.  Why aren't my sessions expiring?
A: In SQLServer mode, session expiration is carried out by the SQL Agent using a registered job.  Make sure your SQL Agent is running.

Q: I have a frameset page which has an HTM extension, and I found out each frame it contains display a different session id on the first request.  Why?
A:The reason is that your frameset page is an HTM file instead of an ASPX file.

In normal case, if the frameset is an aspx file, when you request the page, it will first send the request to the web server, receive an asp.net session cookie (which holds the session id), and then the browser will send individual requests for the frames, and each request will carry the same session id.

However, since your frameset page is an htm file, the first request comes back without any session cookie because the page was serviced by ASP and not ASP.NET.  Then again your browser sends out individual requests for each frame.  But this time each individual request will NOT carry any session id, and so each individual frame will create its own new session.  That's why you will see different session ids in each frame.  The last request that comes back will win by overwriting the cookie written by the previous two requests.  If you do a refresh, you will see them having the same session id.

This behaviour is by-design, and the simple solution is to change your frameset page to .aspx.

Q: I set EnableSessionState to "ReadOnly", but in InProc mode I can still modify the session.  Why is that?
A: Even those enableSessionState is marked as ReadOnly, but in InProc state, the user can still modify the session.  The only difference is that the session will not be locked during the request.  This limitation is by-design.  And I sorry that it’s not documented in MSDN.

Q: I set "cookieless" to true, and now my session variables are lost after a Redirect.  Why?
A: If you're using cookieless, you must use relative path (e.g. ..\hello.aspx) instead of absolute path (e.g. \foo\bar\hello.aspx).  If you use absolute path, ASP.NET cannot preserve your session ID in the URL.

Q: What are the disadvantages of setting cookieless to true?
A: Setting Cookieless=true implies some restrictions, mainly:
1. You cannot use absolute link in your pages.
2. You have to do extra thing to switch between http and https pages in your application.
3. If your customer send a link to a friend, the URL will contain the session ID and both
users could be using the same session ID at the same time.

Q: In InProc mode, I change the timeout value of a session programmatically, and
that causes my Session_End to be called.  Why?
A:It is a a bug of InProc mode.  If you change a session's timeout to a different value,
Session_End will be called (but not Session_Start).  We will looking into that in v2 and
see if we can fix it.

Q: In SqlServer mode, can I store my session state in a database other than tempdb?
A:Yes.  See KB311209.

Q: How can I avoid putting plain password for my sql connection?
A: See sql trusted connection, or put the connection string as encrypted data in the
registry.  For details, KB 329250 and 329290.

Q: What SQL permissions do I need when using SqlServer mode?
A:The caller needs EXEC permission on the following stored procedures in ASPState:

dbo.TempGetAppID
dbo.TempGetStateItem
dbo.TempGetStateItemExclusive
dbo.TempReleaseStateItemExclusive
dbo.TempInsertStateItemLong
dbo.TempInsertStateItemShort
dbo.TempUpdateStateItemLong
dbo.TempUpdateStateItemShort
dbo.TempUpdateStateItemShortNullLong
dbo.TempUpdateStateItemLongNullShort
dbo.TempRemoveStateItem
dbo.TempResetTimeout

For version 1.1, you also need EXEC permission on the following stored procs in
ASPState:

dbo.TempGetStateItem2
dbo.TempGetStateItemExclusive2

Please note that the owner of the sprocs must have SELECT/INSERT/UPDATE/DELETE permissions on the session state tables (dbo.ASPStateTempSessions and dbo.ASPStateTempApplications).  The owner is the account which ran the installsqlstate.sql (or the persistent version (see KB311209)) to install the tables/sprocs/databases needed for sql session state.
Also note that if your session state table lives in tempdb (by default), any permission settings on that table will be lost if you recycle SQL server.

Q: Can I write my own custom session state module?
A: In v1 and v1.1, there are very limited support for writing your own custom session state module.  I can suggest two approaches:
Approach #1 - replace SessionStateModule
In this approach, you write your own custom module and replace the original one in <httpModules>.  This way, you simply roll out your own implementation.
Drawbacks:
i. Since the constructor of HttpSessionState isn't public, you can't create your own
instance of it and stick it to HttpContext like the way ASP.NET SessionStateModule does.  Instead, you have to expose your session through some custom class, and the user can't access it through Page.Session nor HttpContext.Session.
ii. You have to implement all the code to handle session and session id creation/maintenance/expiry, etc.  That can be quite tedious.

Approach #2 - complement SessionStateModule
In this approach, you still rely on original ASP.NET SessionStateModule for session and
session id creation/maintenance/expiry, etc.  But at the same time, you write your own
custom module, and have it subscribed to at least the following HttpApplication events:
(a) PreRequestHandlerExecute - When this event happens, AcquireRequestState has been
fired already, and thus HttpContext.Session is available. In your even handler, you read
your data from your own store and copy them to HttpContext.Session.
(b) PostRequestHandlerExecute - This event is fired before ReleaseRequestState.  Your
event handler will save all the data in HttpContext.Session to your own store, and call
HttpContext.Session.Clear() to remove all items so they won't be saved by ASP.NET
session state.
(c) EndRequest - If an error occurs during the execution of the page,
PostRequestHandlerExecute might be skipped and EndRequest will be fired directly.
Your module might need to do some maintenance work here.
Please note that you shouldn't subscribe to AcquireRequestState and ReleaseRequestState like ASP.NET session state module does because if 2 modules subscribe to an event, there is no guarantee which module will get called first.
Drawbacks:
i. Your custom session data won't be available before PreRequestHandlerExecute and after PostRequestHandlerExecute.
ii. You need to figure out how to cleanup during session expiry or abandonment (in InProc, may piggyback Session_End; hard to resolve in StateServer or SQLServer mode), etc.

In the next major release ASP.NET will increase the support for customizing session state module.  Stay tuned.

Q: How does (de)serialization work in SqlServer and State Server mode?
A: SqlServer and State Server modes use serialization to store objects in a remote store. Understanding how it works will help you write your application correctly.

Assume your page foo.aspx has this piece of code:

line 1    MyClass  class = (MyClass)Session["abc"];
line 2    if (class == null) {
line 3        class = new MyClass();
line 4        Session["abc"] = class;
line 5    }
line 6
line 7    class.LastAccess = DateTime.Now; // This change will reflect in Session["abc"]
line 8
line 9    int total;
line 10  if (Session["def"] == null) {
line 11      total = 0;
line 12  }
line 13
line 14  total = total + 1;
line 15  Session["def"] = total;
line 16  total = total + 100;      // This change will NOT reflect in Session["def"]

First, let me explain one area which confuses many people.

Assume the page hits line 1 and it gets null.  Then the page will create the object (line 3), and put it in session (line 4).  Please note that what Session has is just a reference to your object (and actually the local var 'class' is also just a reference to your object).  So when you modify the object in line 7, you are actually modifying the same object pointed to by Session["abc"].  Bottom line is that 'Session["abc"]' and 'class' are just two references that point to the same object.

However, the situation in line 9-15 is different.  Line 16 has no effect on Session["def"]. It's because 'total' is a value type, and so 'Session["def"]' and 'total' are two integers which are independent of each other.

Please note that the above difference has nothing to do with session state, but with the fundamental difference between a value type (e.g. int), and an object type (e.g. MyClass).  You will have the same behavior if you replace 'Session' by, for example, a hashtable object.

Now, back to the actual question.  When do deserialization and serialization happen?

Assume you hit the above page with a brand new empty session.  After the HttpHandler is done executing your page, ASP.NET will later fire the HttpApplication.ReleaseRequestState event.  At that point, the session state module will go thru all the items in session state, serialize them all into a single binary blob, and save it to a remote store.

Now, when you hit the page again, before HttpHandler execute your page, ASP.NET will fire the HttpApplication.AcquireRequestState event.  At that point, the session state module will read the saved binary blob from the remote store, deserialize it into individual items, and stick them into Session.  But once again, what it puts into Session["abc"] is just a reference to an object (of type MyClass) which was created during the deserialization.

Q: How can I secure my state server?
A: If the state server is running on the same machine as web server, run state server in local only mode by setting the DWORD registry value HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\Param ters\AllowRemoteConnection to 0.  This will prevent remote clients from connecting to the State Server.  This feature is available in v1.1, and in the to-be-shipped v1 SP3.

The state server must be protected by a firewall from external connections to truly guarantee security.  The default port is TCP 42424, although it can be changed by setting HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\Param ters\Port.  Block all external connections on this port except 127.0.0.1 if in local mode, or explicitly disallow all addresses other then the connecting web server if in remote mode.

Using IPSec is another way of protecting your state server.

Q: Can I subscribe to SessionStateModule.End event using a non-global.asax handler method?
A: The answer is NO.  When SessionStateModule raises the End event, only the method
defined in global.asax will be called.

It's limited this way for a technical safety reason.  Suppose asp.net allows a user to use any arbitrary handler to the handle the End event.  In the case, users will usually use a page method as a handler.  When you pass in that handler during event subscription, that handler (unless it's static) is associated with the HttpApplication instance your request is running on.  Please note that HttpApplication instances are recycled to serve other requests.  So later on, when the End event gets fired, asp.net will call the handler, and the HttpApplication instance it is associated with is now being used by another request.  Such a situation will cause all sorts of problem.  So to avoid this danger, in v1 a decision was made to call only the method defined in global.asax.  Hope you all can bear with this limitation.

Q: Can different apps store their session state in different databases on the same SQL server?
A: The answer is yes.  See this KB for more details. http://support.microsoft.com/default.aspx?scid=kb;EN-US;836680

Patrick Y. Ng

ASP.NET Developer

This posting is provided “AS IS” with no warranties, and confers no rights.
- Edited by donkiely on Apr 06, 2005 03:37 PM
- Edited by SonuKapoor on Apr 25, 2005 02:54 AM
- Edited by tmorton on Mar 20, 2012 01:42 PM

gaming wcf

2013-10-09T11:25:00.001-07:00

http://stackoverflow.com/questions/2647218/constraints-when-using-wcf-for-an-online-multiplayer-game

http://programmers.stackexchange.com/questions/148523/chat-game-server-best-way-to-implement-is-wcf-the-way-to-go

http://msdn.microsoft.com/en-us/library/cc297274.aspx

http://blogs.interknowlogy.com/2009/08/05/building-a-really-simple-wcf-p2p-application

http://www.codeproject.com/KB/game/XNASnookerClub.

aspx

http://www.codeproject.com/Articles/515253/Service-Oriented-Architecture-and-WCF

http://msdn.microsoft.com/en-us/library/bb332338.aspx

TAsk Parallel Library:

http://msdn.microsoft.com/en-us/library/dd537609.aspx
http://www.albahari.com/threading/part5.aspx

http://www.codeproject.com/Articles/362996/Multi-core-programming-using-Task-Parallel-Library

REST

http://msdn.microsoft.com/en-us/library/ee391967.aspx

http://www.codeproject.com/Articles/283550/Implementing-5-important-principles-of-REST-using

http://www.codeproject.com/Articles/105273/Create-RESTful-WCF-Service-API-Step-By-Step-Guide
http://msdn.microsoft.com/en-us/magazine/dd315413.aspx

http://www.codeproject.com/KB/game/XNASnookerClub.aspx

http://blogs.interknowlogy.com/2009/08/05/building-a-really-simple-wcf-p2p-application/

interview questions by scott hanselman

2013-10-01T03:25:00.001-07:00

http://www.codeproject.com/Articles/32387/Reply-to-Scott-Henselman-s-Interview-Questions

http://www.hanselman.com/blog/WhatGreatNETDevelopersOughtToKnowMoreNETInterviewQuestions.aspx

http://www.deeptraining.com/litwin/dbdesign/fundamentalsofrelationaldatabasedesign.aspx

http://www.microsoft.com/learning/en-us/course.aspx?id=20465b
http://martinfowler.com/articles/evodb.html

LayeringPrinciples

Martin Fowler

7 January 2005

For the last few days I've been attending a workshop on enterprise software in Norway, hosted by Jimmy Nilsson. During the workshop we had a session where we came up and voted on a bunch of design principles.

The rules were this. Everyone could propose principles for good layering which were added to a list. There was little discussion of the principle - only clarification as needed. People could propose principles they liked or not - the rule was to capture principles that people had heard in the field.

Once we'd got a list, it was time to vote. We used a variant of DotVotingwhere everyone got 10 positive and 10 negative votes.

I've put the results below - principle followed votes in the format positive/negative.

Low coupling between layers, high cohesion within them. 10/0
Separation of concerns. 11/0
Layers should be agnostic of consumers (a layer shouldn't know who's on top of it.) 4/4
Adaptability: be able to change. 2/0
User interface modules should contain no business logic. 10/0
Business logic layers contain no user interface and don't refer to user interface modules. 8/0
No circular references between layers. 8/0
There are at least three main layer types: presentation, domain, and data source. 3/9
Business layer only uses abstractions of technological services. 14/0
Separate development teams by layer. 1/22
Layers should be testable individual. 12/0
Prefer layers to interact only with adjacent layers. 4/4
A layer should be wary of exposing lower layers to upper layers. 1/0
Layers should hide lower layers from upper layers.
Layers should only interact with adjacent layers. 2/3
Changing a lower level layer interface should not change upper layer interfaces. 2/5
Distribute at layer boundaries 0/18
Layers are a logical artifact that does not imply distribution between layers. 11/0
Lower layers should not depend on upper layers. 6/0
Every layer should have a secret. 3/2
Layers should be shy about their internals. 8/0
Layers should be substitutable. 2/0
Layers can have multiple adjacent upper layers. 2/1
Always wrap domain logic with a service layer. 4/5
Rethrow exceptions at layer boundaries. 0/15
Layers should be independently maintainable and versioned. 2/0
Layers should have separate deployment units (eg separate jars or assemblies for each layer). 0/7
Layers may share infrastructural aspects (eg security) 7/0
The domain layer should not talk to external systems - the service layer should do that. 2/3
Inbound external interface modules (eg web service handlers) should not contain business logic. 10/0

Obviously you can't read too much into this list. While it was a good group of people, it was hardly a definitive source of enterprise development expertise. The principles are also worded somewhat loosely and there are overlaps and imprecisions that would be cleaned up if we'd had more than an hour for the exercise. However I suspect the list might provoke a little thought and discussion.

I asked people if there were things that surprised them. A couple of people were surprised that principles that they had heard often (and disliked) were trashed in the voting. (Separate development teams by layer and Rethrow exceptions at layer boundaries.) Similarly there was a surprise that "Business layer only uses abstractions of technological services" got such a strong vote even though it's rarely done in practice.

Continuous Integration

Continuous Integration is a software development practice where members of a team integrate their work frequently, usually each person integrates at least daily - leading to multiple integrations per day. Each integration is verified by an automated build (including test) to detect integration errors as quickly as possible. Many teams find that this approach leads to significantly reduced integration problems and allows a team to develop cohesive software more rapidly. This article is a quick overview of Continuous Integration summarizing the technique and its current usage.

01 May 2006

Martin Fowler

Translations: Portuguese · Chinese ·Korean · French · Chinese · Czech ·

Find similar articles to this by looking at these tags: popular ·agile · delivery · extreme programming · continuous integration

For more information on this, and related topics, take a look at my guide page for delivery.

ThoughtWorks, my employer, offers consulting and support around Continuous Integration. The open source CruiseControl, the first continuous integration server, was originally created at ThoughtWorks. Recently ThoughtWorks Studios, our products group, has released Go - a new server for continuous integration and delivery. It supports parallel, deployment pipelines with multiple projects, a snazzy looking dashboard, and support for automated deployments. It's a commercial tool, but is free to use for small setups.

I vividly remember one of my first sightings of a large software project. I was taking a summer internship at a large English electronics company. My manager, part of the QA group, gave me a tour of a site and we entered a huge depressing warehouse stacked full with cubes. I was told that this project had been in development for a couple of years and was currently integrating, and had been integrating for several months. My guide told me that nobody really knew how long it would take to finish integrating. From this I learned a common story of software projects: integration is a long and unpredictable process.

But this needn't be the way. Most projects done by my colleagues at ThoughtWorks, and by many others around the world, treat integration as a non-event. Any individual developer's work is only a few hours away from a shared project state and can be integrated back into that state in minutes. Any integration errors are found rapidly and can be fixed rapidly.

This contrast isn't the result of an expensive and complex tool. The essence of it lies in the simple practice of everyone on the team integrating frequently, usually daily, against a controlled source code repository.

When I've described this practice to people, I commonly find two reactions: "it can't work (here)" and "doing it won't make much difference". What people find out as they try it is that it's much easier than it sounds, and that it makes a huge difference to development. Thus the third common reaction is "yes we do that - how could you live without it?"

The term 'Continuous Integration' originated with the Extreme Programming development process, as one of its original twelve practices. When I started at ThoughtWorks, as a consultant, I encouraged the project I was working with to use the technique. Matthew Foemmel turned my vague exhortations into solid action and we saw the project go from rare and complex integrations to the non-event I described. Matthew and I wrote up our experience in the original version of this paper, which has been one of the most popular papers on my site.

Although Continuous Integration is a practice that requires no particular tooling to deploy, we've found that it is useful to use a Continuous Integration server. The best known such server is CruiseControl, an open source tool originally built by several people at ThoughtWorks and now maintained by a wide community. Since then several other CI servers have appeared, both open source and commercial - including Cruise from ThoughtWorks Studios.

Building a Feature with Continuous Integration

The easiest way for me to explain what CI is and how it works is to show a quick example of how it works with the development of a small feature. Let's assume I have to do something to a piece of software, it doesn't really matter what the task is, for the moment I'll assume it's small and can be done in a few hours. (We'll explore longer tasks, and other issues later on.)

I begin by taking a copy of the current integrated source onto my local development machine. I do this by using a source code management system by checking out a working copy from the mainline.

The above paragraph will make sense to people who use source code control systems, but be gibberish to those who don't. So let me quickly explain that for the latter. A source code control system keeps all of a project's source code in a repository. The current state of the system is usually referred to as the 'mainline'. At any time a developer can make a controlled copy of the mainline onto their own machine, this is called 'checking out'. The copy on the developer's machine is called a 'working copy'. (Most of the time you actually update your working copy to the mainline - in practice it's the same thing.)

Now I take my working copy and do whatever I need to do to complete my task. This will consist of both altering the production code, and also adding or changing automated tests. Continuous Integration assumes a high degree of tests which are automated into the software: a facility I call self-testing code. Often these use a version of the popular XUnit testing frameworks.

Once I'm done (and usually at various points when I'm working) I carry out an automated build on my development machine. This takes the source code in my working copy, compiles and links it into an executable, and runs the automated tests. Only if it all builds and tests without errors is the overall build considered to be good.

With a good build, I can then think about committing my changes into the repository. The twist, of course, is that other people may, and usually have, made changes to the mainline before I get chance to commit. So first I update my working copy with their changes and rebuild. If their changes clash with my changes, it will manifest as a failure either in the compilation or in the tests. In this case it's my responsibility to fix this and repeat until I can build a working copy that is properly synchronized with the mainline.

Once I have made my own build of a properly synchronized working copy I can then finally commit my changes into the mainline, which then updates the repository.

However my commit doesn't finish my work. At this point we build again, but this time on an integration machine based on the mainline code. Only when this build succeeds can we say that my changes are done. There is always a chance that I missed something on my machine and the repository wasn't properly updated. Only when my committed changes build successfully on the integration is my job done. This integration build can be executed manually by me, or done automatically by Cruise.

If a clash occurs between two developers, it is usually caught when the second developer to commit builds their updated working copy. If not the integration build should fail. Either way the error is detected rapidly. At this point the most important task is to fix it, and get the build working properly again. In a Continuous Integration environment you should never have a failed integration build stay failed for long. A good team should have many correct builds a day. Bad builds do occur from time to time, but should be quickly fixed.

The result of doing this is that there is a stable piece of software that works properly and contains few bugs. Everybody develops off that shared stable base and never gets so far away from that base that it takes very long to integrate back with it. Less time is spent trying to find bugs because they show up quickly.

Practices of Continuous Integration

The story above is the overview of CI and how it works in daily life. Getting all this to work smoothly is obviously rather more than that. I'll focus now on the key practices that make up effective CI.

Maintain a Single Source Repository.

Software projects involve lots of files that need to be orchestrated together to build a product. Keeping track of all of these is a major effort, particularly when there's multiple people involved. So it's not surprising that over the years software development teams have built tools to manage all this. These tools - called Source Code Management tools, configuration management, version control systems, repositories, or various other names - are an integral part of most development projects. The sad and surprising thing is that they aren't part of all projects. It is rare, but I do run into projects that don't use such a system and use some messy combination of local and shared drives.

So as a simple basis make sure you get a decent source code management system. Cost isn't an issue as good quality open-source tools are available. The current open source repository of choice is Subversion. (The older open-source tool CVS is still widely used, and is much better than nothing, but Subversion is the modern choice.) Interestingly as I talk to developers I know most commercial source code management tools are liked less than Subversion. The only tool I've consistently heard people say is worth paying for is Perforce.

Once you get a source code management system, make sure it is the well known place for everyone to go get source code. Nobody should ever ask "where is the foo-whiffle file?" Everything should be in the repository.

Although many teams use repositories a common mistake I see is that they don't put everything in the repository. If people use one they'll put code in there, but everything you need to do a build should be in there including: test scripts, properties files, database schema, install scripts, and third party libraries. I've known projects that check their compilers into the repository (important in the early days of flaky C++ compilers). The basic rule of thumb is that you should be able to walk up to the project with a virgin machine, do a checkout, and be able to fully build the system. Only a minimal amount of things should be on the virgin machine - usually things that are large, complicated to install, and stable. An operating system, Java development environment, or base database system are typical examples.

You must put everything required for a build in the source control system, however you may also put other stuff that people generally work with in there too. IDE configurations are good to put in there because that way it's easy for people to share the same IDE setups.

One of the features of version control systems is that they allow you to create multiple branches, to handle different streams of development. This is a useful, nay essential, feature - but it's frequently overused and gets people into trouble. Keep your use of branches to a minimum. In particular have a mainline: a single branch of the project currently under development. Pretty much everyone should work off this mainline most of the time. (Reasonable branches are bug fixes of prior production releases and temporary experiments.)

In general you should store in source control everything you need to build anything, but nothing that you actually build. Some people do keep the build products in source control, but I consider that to be a smell - an indication of a deeper problem, usually an inability to reliably recreate builds.

Automate the Build

Getting the sources turned into a running system can often be a complicated process involving compilation, moving files around, loading schemas into the databases, and so on. However like most tasks in this part of software development it can be automated - and as a result should be automated. Asking people to type in strange commands or clicking through dialog boxes is a waste of time and a breeding ground for mistakes.

Automated environments for builds are a common feature of systems. The Unix world has had make for decades, the Java community developed Ant, the .NET community has had Nant and now has MSBuild. Make sure you can build and launch your system using these scripts using a single command.

A common mistake is not to include everything in the automated build. The build should include getting the database schema out of the repository and firing it up in the execution environment. I'll elaborate my earlier rule of thumb: anyone should be able to bring in a virgin machine, check the sources out of the repository, issue a single command, and have a running system on their machine.

Build scripts come in various flavors and are often particular to a platform or community, but they don't have to be. Although most of our Java projects use Ant, some have used Ruby (the Ruby Rake system is a very nice build script tool). We got a lot of value from automating an early Microsoft COM project with Ant.

A big build often takes time, you don't want to do all of these steps if you've only made a small change. So a good build tool analyzes what needs to be changed as part of the process. The common way to do this is to check the dates of the source and object files and only compile if the source date is later. Dependencies then get tricky: if one object file changes those that depend on it may also need to be rebuilt. Compilers may handle this kind of thing, or they may not.

Depending on what you need, you may need different kinds of things to be built. You can build a system with or without test code, or with different sets of tests. Some components can be built stand-alone. A build script should allow you to build alternative targets for different cases.

Many of us use IDEs, and most IDEs have some kind of build management process within them. However these files are always proprietary to the IDE and often fragile. Furthermore they need the IDE to work. It's okay for IDE users set up their own project files and use them for individual development. However it's essential to have a master build that is usable on a server and runnable from other scripts. So on a Java project we're okay with having developers build in their IDE, but the master build uses Ant to ensure it can be run on the development server.

Make Your Build Self-Testing

Traditionally a build means compiling, linking, and all the additional stuff required to get a program to execute. A program may run, but that doesn't mean it does the right thing. Modern statically typed languages can catch many bugs, but far more slip through that net.

A good way to catch bugs more quickly and efficiently is to include automated tests in the build process. Testing isn't perfect, of course, but it can catch a lot of bugs - enough to be useful. In particular the rise of Extreme Programming (XP) and Test Driven Development (TDD) have done a great deal to popularize self-testing code and as a result many people have seen the value of the technique.

Regular readers of my work will know that I'm a big fan of both TDD and XP, however I want to stress that neither of these approaches are necessary to gain the benefits of self-testing code. Both of these approaches make a point of writing tests before you write the code that makes them pass - in this mode the tests are as much about exploring the design of the system as they are about bug catching. This is a Good Thing, but it's not necessary for the purposes of Continuous Integration, where we have the weaker requirement of self-testing code. (Although TDD is my preferred way of producing self-testing code.)

For self-testing code you need a suite of automated tests that can check a large part of the code base for bugs. The tests need to be able to be kicked off from a simple command and to be self-checking. The result of running the test suite should indicate if any tests failed. For a build to be self-testing the failure of a test should cause the build to fail.

Over the last few years the rise of TDD has popularized the XUnit family of open-source tools which are ideal for this kind of testing. XUnit tools have proved very valuable to us at ThoughtWorks and I always suggest to people that they use them. These tools, pioneered by Kent Beck, make it very easy for you to set up a fully self-testing environment.

XUnit tools are certainly the starting point for making your code self-testing. You should also look out for other tools that focus on more end-to-end testing, there's quite a range of these out there at the moment including FIT, Selenium, Sahi, Watir,FITnesse, and plenty of others that I'm not trying to comprehensively list here.

Of course you can't count on tests to find everything. As it's often been said: tests don't prove the absence of bugs. However perfection isn't the only point at which you get payback for a self-testing build. Imperfect tests, run frequently, are much better than perfect tests that are never written at all.

Everyone Commits To the Mainline Every Day

Integration is primarily about communication. Integration allows developers to tell other developers about the changes they have made. Frequent communication allows people to know quickly as changes develop.

The one prerequisite for a developer committing to the mainline is that they can correctly build their code. This, of course, includes passing the build tests. As with any commit cycle the developer first updates their working copy to match the mainline, resolves any conflicts with the mainline, then builds on their local machine. If the build passes, then they are free to commit to the mainline.

By doing this frequently, developers quickly find out if there's a conflict between two developers. The key to fixing problems quickly is finding them quickly. With developers committing every few hours a conflict can be detected within a few hours of it occurring, at that point not much has happened and it's easy to resolve. Conflicts that stay undetected for weeks can be very hard to resolve.

The fact that you build when you update your working copy means that you detect compilation conflicts as well as textual conflicts. Since the build is self-testing, you also detect conflicts in the running of the code. The latter conflicts are particularly awkward bugs to find if they sit for a long time undetected in the code. Since there's only a few hours of changes between commits, there's only so many places where the problem could be hiding. Furthermore since not much has changed you can usediff-debugging to help you find the bug.

My general rule of thumb is that every developer should commit to the repository every day. In practice it's often useful if developers commit more frequently than that. The more frequently you commit, the less places you have to look for conflict errors, and the more rapidly you fix conflicts.

Frequent commits encourage developers to break down their work into small chunks of a few hours each. This helps track progress and provides a sense of progress. Often people initially feel they can't do something meaningful in just a few hours, but we've found that mentoring and practice helps them learn.

Every Commit Should Build the Mainline on an Integration Machine

Using daily commits, a team gets frequent tested builds. This ought to mean that the mainline stays in a healthy state. In practice, however, things still do go wrong. One reason is discipline, people not doing an update and build before they commit. Another is environmental differences between developers' machines.

As a result you should ensure that regular builds happen on an integration machine and only if this integration build succeeds should the commit be considered to be done. Since the developer who commits is responsible for this, that developer needs to monitor the mainline build so they can fix it if it breaks. A corollary of this is that you shouldn't go home until the mainline build has passed with any commits you've added late in the day.

There are two main ways I've seen to ensure this: using a manual build or a continuous integration server.

The manual build approach is the simplest one to describe. Essentially it's a similar thing to the local build that a developer does before the commit into the repository. The developer goes to the integration machine, checks out the head of the mainline (which now houses his last commit) and kicks off the integration build. He keeps an eye on its progress, and if the build succeeds he's done with his commit. (Also see Jim Shore's description.)

A continuous integration server acts as a monitor to the repository. Every time a commit against the repository finishes the server automatically checks out the sources onto the integration machine, initiates a build, and notifies the committer of the result of the build. The committer isn't done until she gets the notification - usually an email.

At ThoughtWorks, we're big fans of continuous integration servers - indeed we led the original development of CruiseControl and CruiseControl.NET, the widely used open-source CI servers. Since then we've also built the commercial Cruise CI server. We use a CI server on nearly every project we do and have been very happy with the results.

Not everyone prefers to use a CI server. Jim Shore gave a well argued description of why he prefers the manual approach. I agree with him that CI is much more than just installing some software. All the practices here need to be in play to do Continuous Integration effectively. But equally many teams who do CI well find a CI server to be a helpful tool.

Many organizations do regular builds on a timed schedule, such as every night. This is not the same thing as a continuous build and isn't enough for continuous integration. The whole point of continuous integration is to find problems as soon as you can. Nightly builds mean that bugs lie undetected for a whole day before anyone discovers them. Once they are in the system that long, it takes a long time to find and remove them.

A key part of doing a continuous build is that if the mainline build fails, it needs to be fixed right away. The whole point of working with CI is that you're always developing on a known stable base. It's not a bad thing for the mainline build to break, although if it's happening all the time it suggests people aren't being careful enough about updating and building locally before a commit. When the mainline build does break, however, it's important that it gets fixed fast. To help avoid breaking the mainline you might consider using a pending head.

When teams are introducing CI, often this is one of the hardest things to sort out. Early on a team can struggle to get into the regular habit of working mainline builds, particularly if they are working on an existing code base. Patience and steady application does seem to regularly do the trick, so don't get discouraged.

Keep the Build Fast

The whole point of Continuous Integration is to provide rapid feedback. Nothing sucks the blood of a CI activity more than a build that takes a long time. Here I must admit a certain crotchety old guy amusement at what's considered to be a long build. Most of my colleagues consider a build that takes an hour to be totally unreasonable. I remember teams dreaming that they could get it so fast - and occasionally we still run into cases where it's very hard to get builds to that speed.

For most projects, however, the XP guideline of a ten minute build is perfectly within reason. Most of our modern projects achieve this. It's worth putting in concentrated effort to make it happen, because every minute you reduce off the build time is a minute saved for each developer every time they commit. Since CI demands frequent commits, this adds up to a lot of time.

If you're staring at a one hour build time, then getting to a faster build may seem like a daunting prospect. It can even be daunting to work on a new project and think about how to keep things fast. For enterprise applications, at least, we've found the usual bottleneck is testing - particularly tests that involve external services such as a database.

Probably the most crucial step is to start working on setting up a deployment pipeline. The idea behind a deployment pipeline (also known as build pipeline orstaged build) is that there are in fact multiple builds done in sequence. The commit to the mainline triggers the first build - what I call the commit build. The commit build is the build that's needed when someone commits to the mainline. The commit build is the one that has to be done quickly, as a result it will take a number of shortcuts that will reduce the ability to detect bugs. The trick is to balance the needs of bug finding and speed so that a good commit build is stable enough for other people to work on.

Once the commit build is good then other people can work on the code with confidence. However there are further, slower, tests that you can start to do. Additional machines can run further testing routines on the build that take longer to do.

A simple example of this is a two stage deployment pipeline. The first stage would do the compilation and run tests that are more localized unit tests with the database completely stubbed out. Such tests can run very fast, keeping within the ten minute guideline. However any bugs that involve larger scale interactions, particularly those involving the real database, won't be found. The second stage build runs a different suite of tests that do hit the real database and involve more end-to-end behavior. This suite might take a couple of hours to run.

In this scenario people use the first stage as the commit build and use this as their main CI cycle. The second-stage build runs when it can, picking up the executable from the latest good commit build for further testing. If this secondary build fails, then this may not have the same 'stop everything' quality, but the team does aim to fix such bugs as rapidly as possible, while keeping the commit build running. As in this example, later builds are often pure tests since these days it's usually tests that cause the slowness.

If the secondary build detects a bug, that's a sign that the commit build could do with another test. As much as possible you want to ensure that any later-stage failure leads to new tests in the commit build that would have caught the bug, so the bug stays fixed in the commit build. This way the commit tests are strengthened whenever something gets past them. There are cases where there's no way to build a fast-running test that exposes the bug, so you may decide to only test for that condition in the secondary build. Most of time, fortunately, you can add suitable tests to the commit build.

This example is of a two-stage pipeline, but the basic principle can be extended to any number of later stages. The builds after the commit build can also be done in parallel, so if you have two hours of secondary tests you can improve responsiveness by having two machines that run half the tests each. By using parallel secondary builds like this you can introduce all sorts of further automated testing, including performance testing, into the regular build process.

Test in a Clone of the Production Environment

The point of testing is to flush out, under controlled conditions, any problem that the system will have in production. A significant part of this is the environment within which the production system will run. If you test in a different environment, every difference results in a risk that what happens under test won't happen in production.

As a result you want to set up your test environment to be as exact a mimic of your production environment as possible. Use the same database software, with the same versions, use the same version of operating system. Put all the appropriate libraries that are in the production environment into the test environment, even if the system doesn't actually use them. Use the same IP addresses and ports, run it on the same hardware.

Well, in reality there are limits. If you're writing desktop software it's not practicable to test in a clone of every possible desktop with all the third party software that different people are running. Similarly some production environments may be prohibitively expensive to duplicate (although I've often come across false economies by not duplicating moderately expensive environments). Despite these limits your goal should still be to duplicate the production environment as much as you can, and to understand the risks you are accepting for every difference between test and production.

If you have a pretty simple setup without many awkward communications, you may be able to run your commit build in a mimicked environment. Often, however, you need to use test doubles because systems respond slowly or intermittently. As a result it's common to have a very artificial environment for the commit tests for speed, and use a production clone for secondary testing.

I've noticed a growing interest in using virtualization to make it easy to put together test environments. Virtualized machines can be saved with all the necessary elements baked into the virtualization. It's then relatively straightforward to install the latest build and run tests. Furthermore this can allow you to run multiple tests on one machine, or simulate multiple machines in a network on a single machine. As the performance penalty of virtualization decreases, this option makes more and more sense.

Make it Easy for Anyone to Get the Latest Executable

One of the most difficult parts of software development is making sure that you build the right software. We've found that it's very hard to specify what you want in advance and be correct; people find it much easier to see something that's not quite right and say how it needs to be changed. Agile development processes explicitly expect and take advantage of this part of human behavior.

To help make this work, anyone involved with a software project should be able to get the latest executable and be able to run it: for demonstrations, exploratory testing, or just to see what changed this week.

Doing this is pretty straightforward: make sure there's a well known place where people can find the latest executable. It may be useful to put several executables in such a store. For the very latest you should put the latest executable to pass the commit tests - such an executable should be pretty stable providing the commit suite is reasonably strong.

If you are following a process with well defined iterations, it's usually wise to also put the end of iteration builds there too. Demonstrations, in particular, need software whose features are familiar, so then it's usually worth sacrificing the very latest for something that the demonstrator knows how to operate.

Everyone can see what's happening

Continuous Integration is all about communication, so you want to ensure that everyone can easily see the state of the system and the changes that have been made to it.

One of the most important things to communicate is the state of the mainline build. If you're using Cruise there's a built in web site that will show you if there's a build in progress and what was the state of the last mainline build. Many teams like to make this even more apparent by hooking up a continuous display to the build system - lights that glow green when the build works, or red if it fails are popular. A particularly common touch is red and green lava lamps - not just do these indicate the state of the build, but also how long it's been in that state. Bubbles on a red lamp indicate the build's been broken for too long. Each team makes its own choices on these build sensors - it's good to be playful with your choice (recently I saw someone experimenting with a dancing rabbit.)

If you're using a manual CI process, this visibility is still essential. The monitor of the physical build machine can show the status of the mainline build. Often you have a build token to put on the desk of whoever's currently doing the build (again something silly like a rubber chicken is a good choice). Often people like to make a simple noise on good builds, like ringing a bell.

CI servers' web pages can carry more information than this, of course. Cruise provides an indication not just of who is building, but what changes they made. Cruise also provides a history of changes, allowing team members to get a good sense of recent activity on the project. I know team leads who like to use this to get a sense of what people have been doing and keep a sense of the changes to the system.

Another advantage of using a web site is that those that are not co-located can get a sense of the project's status. In general I prefer to have everyone actively working on a project sitting together, but often there are peripheral people who like to keep an eye on things. It's also useful for groups to aggregate together build information from multiple projects - providing a simple and automated status of different projects.

Good information displays are not only those on a computer screens. One of my favorite displays was for a project that was getting into CI. It had a long history of being unable to make stable builds. We put a calendar on the wall that showed a full year with a small square for each day. Every day the QA group would put a green sticker on the day if they had received one stable build that passed the commit tests, otherwise a red square. Over time the calendar revealed the state of the build process showing a steady improvement until green squares were so common that the calendar disappeared - its purpose fulfilled.

Automate Deployment

To do Continuous Integration you need multiple environments, one to run commit tests, one or more to run secondary tests. Since you are moving executables between these environments multiple times a day, you'll want to do this automatically. So it's important to have scripts that will allow you to deploy the application into any environment easily.

A natural consequence of this is that you should also have scripts that allow you to deploy into production with similar ease. You may not be deploying into production every day (although I've run into projects that do), but automatic deployment helps both speed up the process and reduce errors. It's also a cheap option since it just uses the same capabilities that you use to deploy into test environments.

If you deploy into production one extra automated capability you should consider is automated rollback. Bad things do happen from time to time, and if smelly brown substances hit rotating metal, it's good to be able to quickly go back to the last known good state. Being able to automatically revert also reduces a lot of the tension of deployment, encouraging people to deploy more frequently and thus get new features out to users quickly. (The Ruby on Rails community developed a tool called Capistrano that is a good example of a tool that does this sort of thing.)

In clustered environments I've seen rolling deployments where the new software is deployed to one node at a time, gradually replacing the application over the course of a few hours.

A particularly interesting variation of this that I've come across with public web application is the idea of deploying a trial build to a subset of users. The team then sees how the trial build is used before deciding whether to deploy it to the full user population. This allows you to test out new features and user-interfaces before committing to a final choice. Automated deployment, tied into good CI discipline, is essential to making this work.

Benefits of Continuous Integration

On the whole I think the greatest and most wide ranging benefit of Continuous Integration is reduced risk. My mind still floats back to that early software project I mentioned in my first paragraph. There they were at the end (they hoped) of a long project, yet with no real idea of how long it would be before they were done.

The trouble with deferred integration is that it's very hard to predict how long it will take to do, and worse it's very hard to see how far you are through the process. The result is that you are putting yourself into a complete blind spot right at one of tensest parts of a project - even if you're one of the rare cases where you aren't already late.

Continuous Integration completely finesses this problem. There's no long integration, you completely eliminate the blind spot. At all times you know where you are, what works, what doesn't, the outstanding bugs you have in your system.

Bugs - these are the nasty things that destroy confidence and mess up schedules and reputations. Bugs in deployed software make users angry with you. Bugs in work in progress get in your way, making it harder to get the rest of the software working correctly.

Continuous Integrations doesn't get rid of bugs, but it does make them dramatically easier to find and remove. In this respect it's rather like self-testing code. If you introduce a bug and detect it quickly it's far easier to get rid of. Since you've only changed a small bit of the system, you don't have far to look. Since that bit of the system is the bit you just worked with, it's fresh in your memory - again making it easier to find the bug. You can also use diff debugging - comparing the current version of the system to an earlier one that didn't have the bug.

Bugs are also cumulative. The more bugs you have, the harder it is to remove each one. This is partly because you get bug interactions, where failures show as the result of multiple faults - making each fault harder to find. It's also psychological - people have less energy to find and get rid of bugs when there are many of them - a phenomenon that the Pragmatic Programmers call the Broken Windows syndrome.

As a result projects with Continuous Integration tend to have dramatically less bugs, both in production and in process. However I should stress that the degree of this benefit is directly tied to how good your test suite is. You should find that it's not too difficult to build a test suite that makes a noticeable difference. Usually, however, it takes a while before a team really gets to the low level of bugs that they have the potential to reach. Getting there means constantly working on and improving your tests.

If you have continuous integration, it removes one of the biggest barriers to frequent deployment. Frequent deployment is valuable because it allows your users to get new features more rapidly, to give more rapid feedback on those features, and generally become more collaborative in the development cycle. This helps break down the barriers between customers and development - barriers which I believe are the biggest barriers to successful software development.

Introducing Continuous Integration

So you fancy trying out Continuous Integration - where do you start? The full set of practices I outlined above give you the full benefits - but you don't need to start with all of them.

There's no fixed recipe here - much depends on the nature of your setup and team. But here are a few things that we've learned to get things going.

One of the first steps is to get the build automated. Get everything you need into source control get it so that you can build the whole system with a single command. For many projects this is not a minor undertaking - yet it's essential for any of the other things to work. Initially you may only do build occasionally on demand, or just do an automated nightly build. While these aren't continuous integration an automated nightly build is a fine step on the way.

Introduce some automated testing into your build. Try to identify the major areas where things go wrong and get automated tests to expose those failures. Particularly on an existing project it's hard to get a really good suite of tests going rapidly - it takes time to build tests up. You have to start somewhere though - all those cliches about Rome's build schedule apply.

Try to speed up the commit build. Continuous Integration on a build of a few hours is better than nothing, but getting down to that magic ten minute number is much better. This usually requires some pretty serious surgery on your code base to do as you break dependencies on slow parts of the system.

If you are starting a new project, begin with Continuous Integration from the beginning. Keep an eye on build times and take action as soon as you start going slower than the ten minute rule. By acting quickly you'll make the necessary restructurings before the code base gets so big that it becomes a major pain.

Above all get some help. Find someone who has done Continuous Integration before to help you. Like any new technique it's hard to introduce it when you don't know what the final result looks like. It may cost money to get a mentor, but you'll also pay in lost time and productivity if you don't do it. (Disclaimer / Advert - yes we at ThoughtWorks do some consultancy in this area. After all we've made most of the mistakes that there are to make.)

Final Thoughts

In the years since Matt and I wrote the original paper on this site, Continuous Integration has become a mainstream technique for software development. Hardly any ThoughtWorks projects goes without it - and we see others using CI all over the world. I've hardly ever heard negative things about the approach - unlike some of the more controversial Extreme Programming practices.

If you're not using Continuous Integration I strongly urge you give it a try. If you are, maybe there are some ideas in this article that can help you do it more effectively. We've learned a lot about Continuous Integration in the last few years, I hope there's still more to learn and improve.

For articles on similar topics…

…take a look at the following tags:

Acknowledgments

First and foremost to Kent Beck and my many colleagues on the Chrysler Comprehensive Compensation (C3) project. This was my first chance to see Continuous Integration in action with a meaningful amount of unit tests. It showed me what was possible and gave me an inspiration that led me for many years.

Thanks to Matt Foemmel, Dave Rice, and everyone else who built and maintained Continuous Integration on Atlas. That project was a sign of CI on a larger scale and showed the benefits it made to an existing project.

Paul Julius, Jason Yip, Owen Rodgers, Mike Roberts and many other open source contributors have participated in building some variant of CruiseControl. Although a CI server isn't essential, most teams find it helpful. CruiseControl and other CI servers have played a big part in popularizing and enabling software developers to use Continuous Integration.

One of the reasons I work at ThoughtWorks is to get good access to practical projects done by talented people. Nearly every project I've visited has given tasty morsels of continuous integration information.

Significant Revisions

01 May 2006: Complete rewrite of article to bring it up to date and to clarify the description of the approach.

10 September 2000: Original version published.

entity framework adv/disadvantages

2013-07-24T04:25:00.005-07:00

http://lennilobel.wordpress.com/2009/08/01/rethinking-the-dynamic-sql-vs-stored-procedure-debate-with-linq/

http://www.codeproject.com/Articles/38922/Performance-and-the-Enti

http://www.linkedin.com/groups/Advantages-Disadvantages-Entity-Framework-40949.S.79126661ty-Framework

impersonation and authentication in WCF

2013-05-08T08:09:00.001-07:00

1.Authentication and impersonation are two different concepts. Your request will first reach IIS, authentication involves how IIS check identity of the request and decides if request is eligible, if yes, IIS will delegate the request on to your application, here impersonation is responsible for which role the application is run under. I do not think there is any problem about the authentication process, the complexity comes from impersonation.

2. Default impersonation is turned off, so there is no impersonation, all applications are running using the IIS worker thread. For xp and earlier windows versions, the default user is ASPNET, newer versions the user is Network Service, these are default values, they also can be changed.

3. When impersonation is on, the worker thread will be run under authenticated users or a particular user “TestUser” in the following case:

<identity impersonate="true" username="TestUser" password="P@ssw0rd" />

ASP.NET Compatibility Mode

2013-05-08T07:39:00.001-07:00

http://blogs.msdn.com/b/wenlong/archive/2006/01/23/516041.aspx

Table of Content:

Introduction

ASP.NET HTTP Pipeline

Two Modes

· Mixed Transports Mode

· Under the Hood

ASP.NET Compatibility Mode

· Opt-In for the Mode

· HttpContext.Current

· Globalization

· Impersonation

· Session State

Sample Code

Introduction

The biggest difference between traditional ASMX services and hosted WCF services is probably that the latter can be activated through non-HTTP protocols such as net.tcp and net.pipe by Windows Activation Service (WAS). ASMX services can be only activated through HTTP and they are tightly coupled with ASP.NET HTTP pipeline. And thus many ASP.NET features for ASMX services are HTTP-flavored. Such features include:

Authentication
Url/File authorization
Impersonation
Session state
Request cache
Globalization
Custom HttpModules
Etc

All of these features are related to the following two famous HTTP types:

System.Web.HttpApplication
System.Web.HttpContext

However, WCF services are designed to be transport independent. Even when they are hosted inside ASP.NET applications, the decoupling of the relationship to the HTTP-flavored features is required so that users are not confused. Also most of those ASP.NET features have counterparts in WCF. Nevertheless, WCF provides a mechanism to support smooth migration from ASMX to WCF by introducing two different hosting modes for WCF services:

Mixed Transports Mode
ASP.NET compatibility mode

I will describe these two modes in details in the following.

ASP.NET HTTP Pipeline

Let’s first take a quick look at ASP.NET HTTP pipeline. The following link contains great details about this concept:

HTTP Pipelines: Securely Implement Request Processing, Filtering, and Content Redirection with HTTP Pipelines in ASP.NET

ASP.NET relies on a pipeline of application (HttpApplication), module (IHttpModule), and handler (IHttpHandler) objects to provide flexibility and extensibility. An HTTP request comes into the pipeline and is examined and filtered by the objects and the response is generated and returned through the pipeline. The modules are registered to handle application events from its Init method. Here are some interesting events in the order in which they are raised:

BeginRequest
AuthenticateRequest
PostAuthenticateRequest
AuthorizeRequest
ResolveRequestCache
AcquireRequestState
PreRequestHandlerExecute
[Handlers]
PostRequestHandlerExecute
EndRequest

Modules are registered in the web.config in the <system.web/httpModules> section while handlers are registered in the <system.web/httpHandlers> section. More information about how the events are handled by modules can be found in the following link:

Implementing Intercepting Filter in ASP.NET Using HTTP Module

Besides performing request filtering, modules can also intercept the request from the pipeline by calling HttpApplication.CompleteRequest.

Two Modes

Hosted WCF services can be running in two different modes: Mixed Transports Mode vs ASP.NET Compatibility Mode. This is controlled by the application-level configuration flag “aspNetCompatibilityEnabled”:

<system.serviceModel>

</system.serviceModel>

This flag is false by default and thus WCF services are running in the Mixed Transports Mode. You can also get this flag at runtime from the static property ServiceHostingEnvironment.AspNetCompatibilityEnabled.

Mixed Transports Mode

In this mode, WCF services do not have ASP.NET HTTP-specific features. Instead, all transports are treated in the same way. A WCF service can have multiple endpoints and they can listen on the same or different transports such as HTTP, net.tcp, net.pipe, or net.msmq.

The disabled ASP.NET HTTP features are:

HttpContext.Current: This is always null in this mode. For ASMX services, this is a ThreadStatic property that is stored in the Thread Local Store (TLS). WCF provides a counterpart to this feature: OperationContext.Current.
File/Url Authorization: This transport layer authorization feature is normally enabled through the <system.web/authorization> section in web.config for ASMX sevices. It is disabled in the mixed mode in WCF. You need to use message-level authorization implemented in WCF.
Impersonation: The ASP.NET impersonation feature is normally enabled through the <system.web/identity> section in web.config for ASMX services. It is not available in WCF transport layer in the mixed mode.
Session state: The ASP.NET session state is not supported in the mixed mode. WCF has its own reliable session implementation which provides flexible session state management. The biggest problem for WCF V1 is that the session state does not survive on application recycling and does not work in web garden/farm cases because there is not shared state mechanism between applications or processes which, however, are supported by ASP.NET state service.
Other HTTP features: There are other HTTP features which rely on HttpContext.Current are not supported in the mixed mode naturally. For example, you can not expect that you can get the correct result from ConfigurationManager.AppSettings to work. The globalization feature through <system.web/globalization> is not available.

However, hosted WCF services still rely on ASP.NET to provide the hosting environment, application configuration, and deployment. So the following features apply to all transports:

HostingEnvironment: The ASP.NET provides the hosting environment to WCF services. Accordingly, the settings under <system.web/hostingEnvironment> apply to WCF services.
Compilation system: WCF services are compiled by the BuildManager of ASP.NET. So the settings under <system.web/compilation> controls the compilation of .svc files.

Under the Hood

The ASP.NET compatibility mode is enabled when the aspNetCompatibilityEnabled flag is set to true. I will discuss this in details in the next section. Let’s briefly take a look how the two modes work for HTTP under the hook.

In order to achieve the two modes when hosted in ASP.NET, WCF WebHost layer hooks up into the ASP.NET HTTP pipeline through both module and handler for the HTTP transport. The implementations of both the module and the handler are registered in the machine-wide web.config.

In the mixed mode, the module intercepts the request in the early stage of the pipeline: BeginRequest. When the request comes in, it nulls out HttpContext.Current and reverts the impersonation if the thread is impersonated. Since the request is intercepted at this early stage, other HTTP features are disabled automatically.

In the ASP.NET compatibility mode, however, the module works as a simple request filter. It simply checks the aspNetCompatibilityEnabled flag and skips the request when the flag is true. The handler is finally invoked later in the pipeline to perform the real work for WCF services.

ASP.NET Compatibility Mode

In this mode, WCF services work similarly as ASMX services. That is, all of the existing ASP.NET features are supported in this mode. In this case, it would be confusing to users if other protocols are enabled for the service while those features only work for the HTTP path. So when a WCF service is being activated, the endpoints are checked to ensure that none of them have non-HTTP protocols enabled.

Opt-In for the Mode

Besides the application-level flag aspNetCompatibilityEnabled, users still need to explicitly opt-in for the compatibility mode on the WCF service by using the service attribute AspNetCompatibilityRequirements as following:

[ServiceBehavior]

[AspNetCompatibilityRequirements(RequirementsMode=AspNetCompatibilityRequirementsMode.Allowed)]

class BarService : IHelloContract

{

// ...

}

The RequirementsMode can have three different values: NotAllowed, Allowed, or Required. The default value is NotAllowed. In this way, users have to explicitly design a WCF service to be running in the compatibility mode and understand the disparities for the two different hosting modes.

When the compatibility mode is turned on, most of the ASP.NET features are automatically supported for WCF services, but there are a few special cases need special treatment. I will describe them below.

HttpContext.Current

Users can enjoy this good feature in the compatibility mode as for ASMX services. For example, you can inspect the current request, check the current application settings, and get config information. In ASP.NET 2.0, ConfigurationManager uses HttpContext.Current to retrieve configuration data. So you can use the following features seamlessly:

ConfigurationManager.AppSettings
ConfigurationManager.GetSection (which works the same as HttpContext.Current.GetSection)

WCF has a very flexible threading model to support asynchronous programming. Service operations are usually executed on a different thread than the request thread from ASP.NET. So internally WCF lets HttpContext.Current to flow from thread to thread in the scope of service operations.

Globalization

You can set thread cultures through the Globalization section under <system.web> in web.config. The culture information also flows between thread switches.

Impersonation

ASP.NET supports impersonation (see the link for more details) through the following config setting:

<system.web>

</system.web>

Supporting this for WCF services is a little bit tricky. WCF has its own impersonation mechanism. Here is how you can set the impersonation flag for a WCF operation:

[OperationBehavior(Impersonation = ImpersonationOption.Required)]

public string Hello(string greeting)

{

// ...

}

The ImpersonationOption is a three-value enum just as AspNetCompatibilityRequirementsMode: NotAllowed, Allowed, and Required. The default value is NotAllowed. If it is Allowed, you can turn on service-level impersonation from the following config flag “impersonateCallerForAllOperations”:

</behavior>

There are two cases when a service operation is enabled for WCF impersonation:

The operation has OperationBehavior.Impersonation set to “Required”.
The operation has OperationBehavior.Impersonation set to “Allowed” and the flag “impersonatedCallerForAllOperations” is set to true.

To achieve best user experience, WCF chooses to support impersonation in the compatibility mode in the following combined way:

WCF impersonation always wins over ASP.NET impersonation. That is, if WCF impersonation is enabled for the service operation, the ASP.NET impersonation is ignored. Otherwise, ASP.NET impersonation setting is used.

Session State

The session state feature for ASP.NET is probably the most important reason why people want to run WCF services in the compatibility mode. Even though WCF V1 implements reliable session in the product, the session state is totally in memory and thus it does not survive when the AppDomain is recycled. It is also not persisted across different processes or servers for Web Garden and Web Farm scenarios.

By running WCF services in the compatibility mode, you can enjoy the full functionalities of ASP.NET session state. You can use InProc, or SqlServer, or StateServer modes to handle state persistence. The following link contains good information on how to use ASP.NET session state in different modes:

ASP.NET Session State

By default, WCF does not have cookie enabled on the client side. So when the server requires Cookie, you need to turn on the cookie on the binding for the client through the property HttpTransportBindingElement.AllowCookies.

Sample Code

Here is the sample config for this topic (web.config):

<?xml version="1.0" encoding="utf-8"?>

</appSettings>

<system.web>

</system.web>

<system.serviceModel>

<endpoint binding="basicHttpBinding"bindingConfiguration="BarBinding"

contract="HelloWorld.IHelloContract" />

</service>

</services>

</security>

</binding>

</basicHttpBinding>

</bindings>

<serviceAuthorizationimpersonateCallerForAllOperations="false"/>

</behavior>

</behaviors>

</system.serviceModel>

</configuration>

Here is the service code (Service.svc):

<%@ServiceHost Language = "C#" Debug="true" Service="HelloWorld.BarService"%>

using System;

using System.ServiceModel;

using System.Configuration;

using System.Web;

using System.Web.Configuration;

using System.ServiceModel.Configuration;

using System.Text;

using System.Security.Principal;

namespace HelloWorld

{

[ServiceContract]

public interface IHelloContract

{

[OperationContract]

string WhoIAm();

[OperationContract]

string WhoIAm2();

[OperationContract]

string Hello(string greeting);

}

[ServiceBehavior(InstanceContextMode=InstanceContextMode.PerCall)]

[AspNetCompatibilityRequirements(RequirementsMode=AspNetCompatibilityRequirementsMode.Allowed)]

class BarService : IHelloContract

{

public string WhoIAm()

{

return WindowsIdentity.GetCurrent().Name;

}

[OperationBehavior(Impersonation = ImpersonationOption.Required)]

public string WhoIAm2()

{

return WindowsIdentity.GetCurrent().Name;

}

public string Hello(string greeting)

{

StringBuilder sb = new StringBuilder();

sb.AppendFormat("[From Bar Service] You said: {0}\r\n", greeting);

// Working with AppSettings

sb.AppendFormat("Bob likes the fruit '{0}'\r\n",ConfigurationManager.AppSettings["Fruit"]);

sb.AppendFormat("He also likes the cookie '{0}'\r\n",ConfigurationManager.AppSettings["Cookie"]);

// Working with other config data

BindingsSectionGroup bsg = (BindingsSectionGroup)ConfigurationManager.GetSection("system.serviceModel/bindings");

foreach (BasicHttpBindingElement be inbsg.BasicHttpBinding.Bindings)

sb.AppendFormat("Binding: {0}, MaxReceivedMessageSize: {1}\r\n", be.Name, be.MaxReceivedMessageSize);

// Working with Session state

int myCount = 0;

if (HttpContext.Current.Session["MyCount"] != null)

myCount = (int)HttpContext.Current.Session["MyCount"];

HttpContext.Current.Session["MyCount"] = ++myCount;

sb.AppendFormat("MyCount is '{0}'\r\n", myCount);

return sb.ToString();

}

Here is the client code (Client.cs):

using System;

using System.Collections.Generic;

using System.Text;

using System.Net;

using System.ServiceModel;

namespace HelloWorldClient

{

[ServiceContract]

public interface IHelloContract

{

[OperationContract]

string WhoIAm();

[OperationContract]

string WhoIAm2();

[OperationContract]

string Hello(string greeting);

}

class Program

{

static void Main(string[] args)

{

try

{

if (args.Length != 1) {

Console.WriteLine("Usage: {0} serverUrl",

System.Reflection.Assembly.GetExecutingAssembly().GetName().Name);

return;

}

string fixedUrl = args[0];

HttpTransportBindingElement be = newHttpTransportBindingElement();

be.AuthenticationScheme = AuthenticationSchemes.Negotiate;

be.AllowCookies = true; // Enable cookies

TextMessageEncodingBindingElement tmbe = newTextMessageEncodingBindingElement(MessageVersion.Soap11WSAddressing10,

Encoding.UTF8);

CustomBinding binding = new CustomBinding(tmbe, be);

ChannelFactory<IHelloContract> channelFactory = newChannelFactory<IHelloContract>(

binding, new EndpointAddress(fixedUrl));

IHelloContract clientService = channelFactory.CreateChannel();

Console.Write("Type anything to send: ");

string greeting = Console.ReadLine();

Console.WriteLine("Am I {0}?", clientService.WhoIAm());

Console.WriteLine("Am I {0}?", clientService.WhoIAm2());

for (int i = 0; i < 2; i++)

Console.WriteLine(clientService.Hello(greeting));

((IChannel)clientService).Close();

channelFactory.Close();

}

catch (Exception ex) {

Console.WriteLine(ex.ToString());

}

The output for this sample looks like:

Type anything to send: Howdy

Am I Bill?

[From Bar Service] You said: Howdy

Bob likes the fruit 'Apple'

He also likes the cookie 'Saltine Cracker'

Binding: Binding1, MaxReceivedMessageSize: 30000

Binding: BarBinding, MaxReceivedMessageSize: 65536

MyCount is '1'

[From Bar Service] You said: Howdy

Bob likes the fruit 'Apple'

He also likes the cookie 'Saltine Cracker'

Binding: Binding1, MaxReceivedMessageSize: 30000

Binding: BarBinding, MaxReceivedMessageSize: 65536

MyCount is '2'

Comments

kurakuraninja

18 May 2006 12:20 AM
#
In my blog entry “ASP.NET Compatibility Mode”, I showed how to do impersonation with ASP.NET approach....
kurakuraninja

23 May 2006 1:20 PM
#
Most of customers are asking me about ASP.NET compatability mode and WCF hosting model,wen covered these...
kurakuraninja

11 Feb 2007 11:45 PM
#
In my blog entry “ ASP.NET Compatibility Mode ”, I showed how to perform impersonation with ASP.NET.
kurakuraninja

12 Feb 2007 12:07 AM
#
Virtual Applications and Directories · Process Management model · Application Management model Web.config
kurakuraninja

7 May 2007 11:29 AM
#
Egy végtelenül hosszú linklista következik itt...
kurakuraninja

8 May 2007 5:27 AM
#
¾ Step 1 – Read Principles of Service Design: Patterns and Anti-Patterns for an overview of SOA basics
kurakuraninja

24 May 2007 8:26 AM
#
PingBack from http://mauros.wordpress.com/2007/05/24/links-for-2007-05-24/
kurakuraninja

24 Sep 2007 1:41 PM
#
PingBack from http://blogs.msdn.com/bags/archive/2007/09/24/ajax-q-a-question-7-support-for-asp-net-session-when-calling-wcf-services.aspx
kurakuraninja

24 Sep 2007 1:54 PM
#
PingBack from http://geeks.ms/blogs/roller/archive/2007/09/24/ajax-q-amp-a-question-7-support-for-asp-net-session-when-calling-wcf-services.aspx
kurakuraninja

26 Oct 2007 8:39 PM
#
PingBack from http://ghillie-suits.info/?p=35177
kurakuraninja

5 Jan 2008 5:29 PM
#
I had some cool time working with WCF new features shipped with .net 3.5, one of the most ineteresting...
kurakuraninja

20 Jan 2008 6:28 PM
#
PingBack from http://websitescripts.247blogging.info/wenlong-dongs-blog-aspnet-compatibility-mode/
kurakuraninja

29 Mar 2008 9:18 AM
#
PingBack from http://vincenthomedev.wordpress.com/2008/03/29/accessing-aspnet-session-request-response-httpcontext-httpapplication-in-wcf/
kurakuraninja

20 Jun 2008 2:06 PM
#
I had some cool time working with WCF new features shipped with .net 3.5, one of the most ineteresting
kurakuraninja

26 Jun 2008 3:47 AM
#
PingBack from http://www.komputery.multi5.pl/?p=116
kurakuraninja

17 Jul 2008 8:11 AM
#
¾ Step 1 – Read Principles of Service Design: Patterns and Anti-Patterns for an overview of SOA basics
kurakuraninja

17 Jul 2008 8:41 AM
#
¾ Step 1 – Read Principles of Service Design: Patterns and Anti-Patterns for an overview
kurakuraninja

8 Apr 2009 10:24 AM
#
It is very common for WCF services that work as Ajax callbacks and ASP.NET pages that live in the same
kurakuraninja

15 Apr 2009 11:35 PM
#
Here is a blog entry from Wenlong Dong's blog which explains the "ASP.NET Compatibility Mode" in WCF:
kurakuraninja

16 Apr 2009 1:09 AM
#
PingBack from http://www.codedstyle.com/wcfgood-article-explaining-the-aspnetcompatibilityenabled-of-iis-hosted-application-3/
kurakuraninja

16 Apr 2009 1:11 AM
#
PingBack from http://www.codedstyle.com/wcfgood-article-explaining-the-aspnetcompatibilityenabled-of-iis-hosted-application-6/
kurakuraninja

16 Apr 2009 1:54 PM
#
PingBack from http://www.codedstyle.com/wcfgood-article-explaining-the-aspnetcompatibilityenabled-of-iis-hosted-application-2/
kurakuraninja

29 May 2009 12:51 PM
#
PingBack from http://paidsurveyshub.info/story.php?title=wenlong-dong-s-blog-asp-net-compatibility-mode
kurakuraninja

1 Jun 2009 7:13 AM
#
PingBack from http://portablegreenhousesite.info/story.php?id=12193
kurakuraninja

9 Jun 2009 9:02 PM
#
PingBack from http://insomniacuresite.info/story.php?id=5070
kurakuraninja

14 Jun 2009 3:02 AM
#
PingBack from http://gardendecordesign.info/story.php?id=2920
kurakuraninja

16 Jun 2009 9:53 PM
#
PingBack from http://fixmycrediteasily.info/story.php?id=1244
Sohel

25 May 2010 4:11 AM
#
Nice explanation. Thanks for sharing..
Arien

25 Jun 2012 11:27 PM
#
Very good! I wish I read this before

versioning in WCF

2013-05-07T01:49:00.001-07:00

http://msdn.microsoft.com/en-us/library/ms731060.aspx

http://devproconnections.com/development/versioning-wcf-services-part-

1. http://devproconnections.com/development/versioning-wcf-services-part-i

2. http://msdn.microsoft.com/en-us/library/ms731060.aspx

3. I collection , as Ienumerable should be having key value pair, but in records data depend on the key ,but has more no of values.

4. Is it about instancing or concurrency , I am not clear. Or it can be synchronous/async

5. By using Transactionscope attribute http://www.codeproject.com/Articles/38793/6-Steps-to-Enable-Transactions-in-WCF

6. SPs once compiled will not complile again until it is altered.

1) If Client consuming WCF hosted service if we changed anything in method how client notify that changes ?

2) If you have collection of records which one is more use full in IEnumrable / ICollection .

3) If two clients are consuming service if we want implement scope of access of service then how can you do this .

4) Do u know how to implement TRANSACTION in WCF Service .

5) If you have Stored procedure and one transaction on SP got over and control came out of scope . if again want to action using SP will it compile again or not ?

convert web app to mobile app

2013-05-02T11:31:00.001-07:00

http://stackoverflow.com/questions/743348/is-it-possible-to-convert-web-application-to-mobile-application

http://www.tothepc.com/archives/5-ways-to-create-or-convert-into-mobile-phone-website/

http://www.google.com/gwt/n -- then type the url ur app will be converted to mobile app

architecting .Net applications

2013-01-29T22:33:00.001-08:00

http://petermeinl.wordpress.com/2011/04/10/my-advice-for-net-application-architectures/

http://www.codeproject.com/Articles/30378/Architecting-NET-Web-Applications-for-Scale-Perfor

http://blogs.msdn.com/b/willy-peter_schaub/archive/2010/05/29/visual-studio-2010-architecture-guidance-what-is-a-4-1-view.aspx

http://www.asp.net/web-forms/tutorials/deployment/deploying-web-applications-in-enterprise-scenarios/enterprise-web-deployment-scenario-overview

Position: Manager Technology Location - Bangalore Key Responsibilities Architecture & Design Responsible for design and architecture of the project and works with design team and Clients to create the needed artifacts Responsible for creating the Non functional requirements based on the business needs Responsible for choosing the needed technology stack based on the functional, non-functional requirements and based on other factors like client drivers, environment and feasibility For package implementations, perform the gap analysis between business requirements and the package features and design the configuration, customizations, extensions, interfaces required to meet the requirements Responsible for identifying and designing dependencies with other systems in the enterprise Development & Support Responsible for consistency, high quality and adherence to applicable Sapient and/or client standards in solution delivery Establishes steps of doneness for various types of activities that are done during EAR, Development and Maintenance phases of a project. For package implementations, helps create best practices/approaches to be leveraged by the team. Drives setup of the different environment (development, test stage etc) Responsible for ensuring that technical solution meets performance, reliability and other Ã¢â‚¬Å"ilityÃ¢â‚¬ requirements Troubleshoot complex technical issues on projects Planning Tracking & Estimation Works with the Project Manager to create the estimate and plans for projects and decompose them among the various tracks Can actively identify, manage, quantify and escalate risks to various internal and external stakeholders Partners with Project Manager and clients to establish Scope Management Process Evaluates the LOE, complexity and risks associated in adding scope it Client Management Represent the organization in customer-facing communication pertinent to SapientÃ¢â‚¬â„¢s technical expertise on the specific platform Interacts with multiple clients (client senior developers and architects) to create technology

specifications from the business issues/requirements at an application level Identifies choices and tradeoffs involved in designing and implementing a solution and communicates them to the client. Raises and drives resolution for all technical design and implementation issues in the module with the client Adherence to Processes Is well versed in relevant methodology, processes, tools and technology standards and can effectively chose relevant parts needed for the project Works with the Project Manager and the Track leads to manage the process compliance and monitor the quality of work Provides mentoring on best practices to teams Documentation Is well versed with different ways to document requirements, design and architecture and can chose the right artifacts needed during a project Defines and assesses completeness and quality of documents/artifacts Team Management Manage along with a Project manager a small to medium sized team and resolve issues and dependencies in the team. Review the key objectives of projects and clarify the linkage of tasks to the overall objectives Responsible for performance assessment and working with the team for creating growth plans Effectively communicate with the team on a periodic basis the company strategy, important events Coach and mentor the team to help deliver to the client expectation Actively participate in, and assists with, company events such as hiring, training and internal initiatives. Drive knowledge sharing lessons learned from project experiences Competency Profile dotNET, Client Management, dotNET - ORM, dotNET - Development LanguagesSQL Server Development - T-SQL, AJAX, ASP / dotNET , JavaScript / DHTML, VB Script Windows Forms Applications, Windows Presentation Foundation, dotNET - Integration Technologies, Enterprise Architecture Planning (REAP), Planning/ Execution & Tracking Scoping and Estimating, Data Modeling, High Availability and Failover Applications Logical Architecture Design, OOAD and UML, Package / Vendor Selection Performance / Capacity Planning

Entity frame work architecture

2012-12-06T06:11:00.002-08:00

http://en.wikipedia.org/wiki/ADO.NET_Entity_Framework

Learn .Net

2012-11-29T22:05:00.000-08:00

http://msdn.microsoft.com/en-us/vstudio/aa496123 -- Learn .Net

http://msdn.microsoft.com/library/vstudio/hh156542

SubVersion

2012-11-28T23:37:00.000-08:00

http://pythonconquerstheuniverse.wordpress.com/2011/03/16/learning-subversion-the-mystery-of-svn-2/

https://ariejan.net/2006/11/24/svn-how-to-structure-your-repository

Service Locator Pattern --a specilised version of Inversion of control

2012-11-27T22:57:00.001-08:00

http://www.martinfowler.com/articles/injection.html

Use the Service Locator pattern to achieve any of the following objectives:

You want to decouple your classes from their dependencies so that these dependencies can be replaced or updated with little or no change to the classes.
You want to write logic that depends on classes whose concrete implementation is not known at compile time.
You want to be able to test your classes in isolation, without the dependencies.
You do not want the logic that locates and manages the dependencies to be in your classes.
You want to divide your application into loosely coupled modules that can be independently developed, tested, versioned, and deployed.

Solution

Create a service locator that contains references to the services and that encapsulates the logic that locates them. In your classes, use the service locator to obtain service instances. The following diagram illustrates how classes use a service locator.

How classes use a service locator

The Service Locator pattern does not describe how to instantiate the services. It describes a way to register services and locate them. Typically, the Service Locator pattern is combined with the Factory pattern and/or the Dependency Injection pattern. This combination allows a service locator to create instances of services.

Example;
In Business we used the wcf.Unity and wcf service host factory

Repository Pattern

2012-11-27T22:54:00.000-08:00

The Repository Pattern is a common construct to avoid duplication of data access logic throughout our application. This includes direct access to a database, ORM, WCF dataservices, xml files and so on. The sole purpose of the repository is to hide the nitty gritty details of accessing the data. We can easily query the repository for data objects, without having to know how to provide things like a connection string. The repository behaves like a freely available in-memory data collection to which we can add, delete and update objects.
The Repository pattern adds a separation layer between the data and domain layers of an application. It also makes the data access parts of an application better testable.

Use the Repository pattern to achieve one or more of the following objectives:

You want to maximize the amount of code that can be tested with automation and to isolate the data layer to support unit testing.
You access the data source from many locations and want to apply centrally managed, consistent access rules and logic.
You want to implement and centralize a caching strategy for the data source.
You want to improve the code's maintainability and readability by separating business logic from data or service access logic.
You want to use business entities that are strongly typed so that you can identify problems at compile time instead of at run time.
You want to associate a behavior with the related data. For example, you want to calculate fields or enforce complex relationships or business rules between the data elements within an entity.
You want to apply a domain model to simplify complex business logic.

Use a repository to separate the logic that retrieves the data and maps it to the entity model from the business logic that acts on the model. The business logic should be agnostic to the type of data that comprises the data source layer. For example, the data source layer can be a database, a SharePoint list, or a Web service.
The repository mediates between the data source layer and the business layers of the application. It queries the data source for the data, maps the data from the data source to a business entity, and persists changes in the business entity to the data source. A repository separates the business logic from the interactions with the underlying data source or Web service. The separation between the data and business tiers has three benefits:

It centralizes the data logic or Web service access logic.
It provides a substitution point for the unit tests.
It provides a flexible architecture that can be adapted as the overall design of the application evolves.

Repositories are bridges between data and operations that are in different domains. A common case is mapping from a domain where data is weakly typed, such as a database or SharePoint list, into a domain where objects are strongly typed, such as a domain entity model.

Repositories often use the Data Mapper pattern to translate between representations.

project 2010

2012-11-06T03:08:00.002-08:00

http://cdn-smooth.ms-studiosmedia.com/msstudios/1005/1003463/Mod_2_Planning_Design_and_Deployment/Default.html

http://www.brighthubpm.com/agile/124334-a-guide-to-agile-project-management/

Architect’s Class

2012-11-06T02:37:00.002-08:00

Architect's Master Class

   Home     Services      Industry Leadership      About IDesign      Customers      Downloads      Contact Us


The Architect’s Master Class
Overview
While many developers and managers have a clear idea regarding the characteristics, practices, and corresponding set of responsibilities of their roles, the picture is often vague when it comes to software architects. What is the single most important task facing the software architect? What is the division of labor and responsibilities between the architect and the project manager? How much the architecture should be tied in to the particulars of the underlying technology used, or for that matter, for the specifics of the business? Where is the hand-off point between the architect and the developers? What are the necessary skills and analysis tools employed by an architect? How do you validate the design before construction begins? How do methodologies such as service-orientation affect the design and development process? What are software architecture's best practices, guidelines and pitfalls? How do you go about designing world-class systems? How do you make the transition from abstract design patterns and concepts to concrete development decisions? How does the architect decompose the system into its sub system and modules?
IDesign's flagship offering, the Architect’s Master Class, is the ultimate resource for the professional architect.
The class answers the above questions and more, and teaches the architect how to take an active leadership role in process, design, and technology. You will learn how to lead your team through the use of effective software processes, how to best leverage key technologies for the implementation of Service Oriented Architectures (SOA), and how to apply the IDesign Method™.
This 5 days training class is conducted by a Master Architect who shares his vast experience and perspective with the students, imparting both knowledge and insight, ensuring your success as a modern software architect. The IDesign Master architect will provide the common foundation required by software architects, both technical and soft skills. The class sets the focus on the why and the rationale behind particular design decisions, often shedding light on poorly understood aspects.
Noteworthy is that this class is called the Architect’s Master Class (as opposed to the Architecture Master Class) because it is dedicated to the core body of knowledge required of today’s modern software architects, knowledge that transcends mere design patterns and architecture. The core body of knowledge comprises of three elements: development process, technology, and finally analysis & design. The class shows the architect how to take an active leadership role on all three aspects, as a continuum, since in order to deliver high-quality, affordable solutions, one cannot separate process from design from technology – all three have to work in concert. The class also points out classic mistakes and risk mitigations across the process, technology and design. The agenda reflects these three elements. The first part is devoted to the accompanying service-oriented development process and the required project management skills. The second part is an immersion in key modern design patterns and development skills, using WCF as a reference model, as a way of illustrating the design ideas and best practices, ensuring the architect is a qualified technical lead.. This section of the class also includes a detailed projection of the next platform after .NET, and how to best prepare for it.
In the last part the IDesign architect will explain the IDesign original approach to large system analysis and design called the IDesign Method - a breakthrough, battle-proven approach to software architecture providing a significant reduction in the effort and time required for architecting, designing, and implementing software solutions. The IDesign Method distils the IDesign's accumulative lessons learned over more than a decade of architecting systems across numerous projects, industries, countries, and teams. The IDesign Method has three elements: it is a method for decomposing a system into modules or services based on the system top-level uses cases, the IDesign Method offers a set of very simple design notations to capture the design decisions, and a near-mechanical approach for automating the design decision of rarely discussed topics such as allocation of services to assemblies, allocation of services to processes, transaction boundaries, identity management, authorization and authentication boundaries, synchronization and more. To demonstrate the IDesign Method in action, the Architect Master Class will conclude in an interactive design session where the Master Architect will use the IDesign Method on a system provided by the students (a short version of what we focus on in our Architecture Clinics).
In the class you will also receive the IDesign documents and diagram templates, tools and samples, and reference projects.
Don’t miss on this unique opportunity to learn and improve your architecture skills with IDesign, and share our passion for architecture and software engineering, gain from our experience of numerous design projects and profound insight on architecture, technology and its applications.
Target Audience
Any .NET architect, project lead or senior developer would benefit greatly from the class.
Duration
5 very intense days.
Outline
The Architect
Software development as engineering
Types of architects
The role of the architect
Architects and technology
Architects and the business
Service-Oriented Development Process
Project planning
Estimation and tracking
Documentation
Requirement management and traceability
Configuration management
Quality control
Design for performance
Services simulation and emulation
Peer reviews
Development standards
Metrics collection
Visibility management
Introduction to Service-Orientation
Why service orientation
Service-oriented architecture
Service-oriented applications
WCF Essentials
Service-oriented programming
WCF architecture
Implementation considerations
Service Contract Design and Factoring
Service contract design
Contract factoring techniques
Contract metrics
Service-Oriented Design Patterns and Best Practices
Data contracts and data contracts versioning
Instance management and throttling
Operations and event management
Service discovery
Windows Azure AppFabric service bus
Transaction management and consistency
Concurrent management, responsiveness and availability
Design for security
Service Granularity
Every class as a service?
Performance consideration and perspective
WCF benchmarks
Beyond .NET and WCF
The future platform
Design and Architecture
The IDesign Method
Service decomposition
Use cases analysis
Assembly allocation
Run-time processes design
Identity management
Authentication
Authorization
Transaction flow
Synchronization
The Method in Action
The interview thought process
Use cases analysis
Service decomposition
Architecture diagrams
Process Groupthink
What about Monday
The pitfall of Groupthink
Architect as agent of change
Upcoming Classes
November 12-16, Los Gatos, CA (Register now to secure a seat!)
December 10-14, Belgium
February 25-March 1, Sydney, Australia
April 22-26, London, United Kingdom
Subscribe to the offerings feed
Testimonials
After taking the WCF Master Class last year, I felt the Architects Master Class would be the perfect follow up to take things to the next level. This class is light years ahead of the industry in terms of content and the sheer volume of knowledge the IDesign team presented. It’s a unique experience to be able to see the world through the eyes of world class architects, learn their techniques and way of thinking.
Stuart Snaddon
Software Engineer
United Kingdom

--------------------------------------------------------------------------------

IDesign’s Architect’s class is far and away the best training class I have ever taken. It transcends technological trends and gives you practical knowledge that will be useful for almost any platform and for the rest of your career. Easily the best thing I've spent my money on in quite a while.
Geoff Heeren
Lead Architect
Emportal

--------------------------------------------------------------------------------

The Architect’s Master Class rigorous approach to software design and development will enable you to engage in software architecture as an engineering discipline. I can see how my past failures could have been prevented if I had applied the IDesign method. My understanding of what the software architect is actually supposed to do has been clarified and reshaped by the class. The IDesign Architect’s Master Class is an essential part of any software architect’s training. You should not in good conscience call yourself a software architect if you don’t posses the skills and techniques presented in the class.
Russ Ferrill
Software Engineer
Vendor Safe Technologies

--------------------------------------------------------------------------------

Attending the Architect Master Class by Juval Lowy was simply the most rewarding professional experience of my career. The material was a world class combination of methodology, process, and technology that no one else in the industry is teaching. Juval’s extensive experience and knowledge base allowed him to present the material in a historical context that changed my perspective on current technologies in ways I did not previously think possible. I also thoroughly enjoyed Juval’s witty presentation style which kept me on my toes and, more importantly for such an intense class, kept my attention firmly focused. I now feel more prepared than ever to take my career to new heights and continue to build upon my newfound knowledge. I would recommend this class to any serious Architect looking for that elusive next level of enlightenment. Thank you Juval!
Joe Crabtree
Solutions Architect
SharePoint360

--------------------------------------------------------------------------------

It has to be the most influential and profound course I have ever undertaken; it has given me a depth and breadth of knowledge that was unbelievable.
Robert Dyball
WorkCover NSW

--------------------------------------------------------------------------------

Wanted to thank you for the highly impressive Architect’s Master Class.
I have never walked out of any training, whatsoever, so stunned as walking out of this. It has the exact mixture of practical and theoretical content. My only regret is that it didn't last longer :)
I have already started talking with our project managers and architects about process leadership and the role of an architect.
Thanks Again,
Ally Pearl
SharePoint Consultant
OBS

--------------------------------------------------------------------------------

The Architect’s Master course was the single most relevant and useful professional training I’ve ever attended. Juval brings his deep experience and Zen master-like wisdom to the class and makes it easy to apply the lessons to real world scenarios. If you are lucky enough to attend, you will emerge from the class, a lean, mean, service-oriented machine.
David Carrico
System Architect
ITG

--------------------------------------------------------------------------------

Thanks for sharing your wisdom and experience to us and it was the best technical class I have ever attended. You have provided answers to many of the lingering questions I used to have and that too without me asking all these questions, again it was wonderful and enchanting class.
Manoj Garg
FIS Global

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I just wanted to thank IDesign for the class, Brian for teaching it, and Juval for promoting it to me. I used things it taught me immediately in my work and found the ideas presented to be quite excellent. I would even say those that gave testimonials were not blowing smoke on this whatsoever. If anything they are underselling it. I started architecting my current system based on your methods, and am finding it to be a really intelligent way to go about my work. Juval, everything you said is coming out in spades. I feel I can handle pretty much anything that is thrown at me and I will create a great system for my company. Thanks again for the class and the ideas presented.
Steve Portock
Software Architect
St. Louis, Missouri

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IDesign has a unique way of presenting the design alternatives and narrowing them down to the best practices. The Architect's Master Class will teach you everything you need to know about architecting and building service-oriented applications. Not only will you walk away with a great learning experience, you will also have a host of tools and examples that you can put to work in your applications right away. This alone saved us months of development time and effort.
Michael Marchiondo
Spectrum Technology Consultants
Columbus, OH

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The incredible amount of experience and knowledge presented during the Architect’s Master class, in a few unbelievable days, has completely changed the way I think about software architecture. One of the main takeaways is the IDesign Method which is simple and effective was of designing systems. The method is so clear, simple and to the point that it can be implemented into our existing or future projects immediately, improving project schedules and increasing quality.
Camilo Orozco
Bioinformatics Programmer
GNF

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I wanted to let you know how impressed I was with the Architect’s Master Class. I have had a somewhat chequered career and for the last ten years or so have been in IT. During that time, I have attended more lectures, training courses and conferences than I care to count, but never have I walked out of any them as affected as last week left me. The course was entertaining, enormously thought provoking and yet, still managed to walk that fine line between theoretical and practical content. More importantly, it reignited my enthusiasm for the industry and my role in it. In addition, I will be seriously adopting the IDesign process for a project that we are just commencing. It is also the case that the knowledge that you divulged during the course will form part of our core architectural direction over the coming few years; in particular, your ‘every class as a service’ approach has ignited a great deal of curiosity and excitement amongst our senior developers!
Thanks Again,
Malcolm Young
General Manager, Architecture and Technology
F1 Solutions

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The IDesign Architect’s Master class was first rate. I never thought it was possible to learn so much in a few days, and my only regret is that the class was not longer. Juval’s clarity of thinking, precise examples, and anecdotal information has enabled me to start thinking more like a software architect. I highly recommended for anyone contemplating an architecture career or needing to work closely with architects.
Blair Shaw
Senior Consultant
Microsoft Partner Services
Redmond, Washington

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The IDesign Architect's Master Class is a true awakening. Juval spoke candidly about our software development crisis and presented his insight and solutions. His incredible knowledge of the software development history and methodical analysis of its evolution and future enlighten and inspire me. I am eager to apply the IDesign Method and WCF in our future projects along with the IDesign effective software development process using the templates for project management, top-level design, and share these techniques with management and fellow developers at Circle K.
Chao-Sha Huang
Senior Software Engineer
Circle K Stores

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The class was a mind blower, and a perfect educational complement to the WCF class. Juval was on fire. By the end of the week he had led the discussion beyond skills and techniques to address the larger concerns of professional and personal responsibility, which was truly inspirational. (And daunting. He sets the bar so high.)
Steve Taylor
Technical Lead
HEA Consulting

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Software architecture is engineering. Design and development of software systems must be done using a methodology that demystifies the process, reigns in technology and complexity and enables the teams’ productivity. The Architect’s Masters Class targets precisely these goals. The curriculum is built from Juval’s amazing in-depth understanding of architecture and original analysis techniques along with years of actual experience. All elements give architects the skills to deliver successfully on quality, on schedule, on budget, on features, for now and as the system evolve. I consider this the graduate class for real world Architects charged with providing solutions to real world businesses.
Joshua Dees
VP of MIS
Black Diamond Equipment Ltd.

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For anyone who has ever wondered if there is a better way of creating software, the Architect’s Master Class is nothing short of a revelation. Juval Löwy systematically demolishes (seemingly) all conventional-wisdom of software best-practice with precision, contextual honesty and reasoned argument; by the end of the first day you can already feel your consciousness being raised to a level you never knew existed. At the same time, he deconstructs each of his original teaching modules with crystal-clarity, coupled with the wit and good-humour of a master raconteur. As such, your attention is held with relentless focus for five gruelling days, during which Juval takes it upon himself to instil in you his vast experience as a world-class engineer. Microsoft recognizes him as a ‘Software Legend’, but to anyone who wants to be the best they can be, he is simply the Maestro.
Dr Riccardo Bennett-Lovsey
Senior Programmer Analyst
London, UK

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Simply put, the IDesign alumni that referred me to the Architect's Master Class described it as "career-altering," and he is not one for hyperbole. The class was the finest 5-day training I have been to in the last 10 years. Most classes focus only on technology, and by the end of day 5 you want to poke your eyes out with your laptop. The Architect's Master Class on the other hand, I could've done for another week. In fact, I will be back for your clinic next March. I have the benefit of having excellent sponsors that fully support my professional development, and that of my team. When I told them about the class and the clinic, they said "go!"
Ted Assur
IT Solutions Architect
Providence Health & Services

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I wanted to thank you for a (professional) life changing week. Usually I can't sit at class more than 50% of the time - it is boring and they don't teach me anything I couldn't teach myself or already know. In the Architect's Master Class I set for 9 hours a day and couldn't have enough of it: I learned what are my responsibilities as an architect (I thought the architect is only the software designer), the engineering aspect of software, the importance of delivering not only on time but also on budget and on quality, not to wait to "grow" to be an architect but to manage my career, and how to quantify and measure what I previously considered as hunches. I have much more insight from this week and many pieces are in place now. I can't wait to attend the Architecture Clinic and the other Master Classes.
Itai Zolberg
Software Architect
Tel Aviv, Israel

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I want to thank you again for the Architect's Master Class. You took me apart and put me back together again. I have known for years that the best way to do class design is to encapsulate what will change--that's what design patterns are all about. And yet it has eluded me for so long that this same concept is to be applied to architecture. It is so simple, so elegant, and was right under my nose for all of this time. I have been looking through the IDesign Alumni forum and it is an absolute gold mine, a treasure trove of knowledge and experience. Access to this alone is well worth the cost of the class. Taking the Architect's Master Class has been one of the few defining inflection points in my career. I have been searching for this material for years and have come up empty handed so many times. Thank you for putting this material together, for teaching it and for pushing our profession (and passion) towards a legitimate engineering discipline. I look forward to hearing from you on the forums and in upcoming clinics.
Cris Zamora
Senior Architect and Project Lead
Seamless
Salt Lake City, UT

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© 2012 IDesign, Inc. All rights reserved. | Hosted by OrcsWeb.

Tools Used

2012-10-18T21:50:00.000-07:00

Fiddler:
Fiddler is a Web Debugging Proxy which logs all HTTP(S) traffic between your computer and the Internet. Fiddler allows you to inspect traffic, set breakpoints, and "fiddle" with incoming or outgoing data. Fiddler includes a powerful event-based scripting subsystem, and can be extended using any .NET language.
Fiddler is freeware and can debug traffic from virtually any application that supports a proxy, including Internet Explorer, Google Chrome, Apple Safari, Mozilla Firefox, Opera, and thousands more. You can also debug traffic from popular devices like Windows Phone, iPod/iPad, and others.
To debug applications you've written in Java, .NET, or using WinHTTP

Presentation skills

2012-10-17T23:57:00.001-07:00

http://focs.wordpress.com/2007/09/12/9-tips-how-to-give-a-technical-presentation/

Practice a lot, dont read , say it from your heart, speak slowly and clearly,
each presentation have a climax and a start up.

Biztalk

50 general interview questions

Editors Picks

http://www.sqlservercurry.com/2013/11/sql-server-database-unit-testing-using_16.html

The core team -Project Management Foundations

Project Management Foundations - The Core Team

What Is the Purpose of the Core Team?

What Are the Important Elements of a Good Core Team?

Procuring the Core Team Members

On-boarding the Core Team

Core Team Best Practices

The Project Design Master Class -PMP

Overview

Target Audience

Duration

Project Design Method Overview

Essential Concepts

Project Compression

Quantifying Risk

Project Design in Action

Project Design Mini-Clinic

practice interview questions 2

ABOUT SCOTT

practice interview questions

ABOUT SCOTT

practice interview questions

ABOUT SCOTT

Understanding session state modes in asp.net

Understanding session state modes + FAQ

This site is managed for Microsoft by Neudesic, LLC. | © 2013 Microsoft. All rights reserved.

gaming wcf

interview questions by scott hanselman

Continuous Integration

Contents

Building a Feature with Continuous Integration

Practices of Continuous Integration

Maintain a Single Source Repository.

Automate the Build

Make Your Build Self-Testing

Everyone Commits To the Mainline Every Day

Every Commit Should Build the Mainline on an Integration Machine

Keep the Build Fast

Test in a Clone of the Production Environment

Make it Easy for Anyone to Get the Latest Executable

Everyone can see what's happening

Automate Deployment

Benefits of Continuous Integration

Introducing Continuous Integration

Final Thoughts

Further Reading

For articles on similar topics…

Acknowledgments

Significant Revisions

Guides

Popular Articles

Books

Site Sections

ThoughtWorks

entity framework adv/disadvantages

impersonation and authentication in WCF

ASP.NET Compatibility Mode

Session State

versioning in WCF

convert web app to mobile app

architecting .Net applications

Entity frame work architecture

Learn .Net

SubVersion

Service Locator Pattern --a specilised version of Inversion of control

Solution

Repository Pattern

project 2010

Architect’s Class

Tools Used

Presentation skills