5pm Posts

When not to use method overload

noreply@blogger.com (Saket Porwal) — Wed, 05 Aug 2009 20:02:00 +0000

Method overloading is taught in OOP 101, but there are times when it should be avoided like plague. Let me explain ...

During a recent implementation of Caching solution, I had to create a CacheManager which could support the creation and management of different types of Cache types - say file system based, memory based, db based etc. Each cache type comes with different options. For example, file based system could monitor a file as a dependency, which the DB based cache does not.

A typical example of different overloads is as follows ...

interface ICache {

    void Add<T>(string key, T value)

    void Add<T>(string key, T value, string filename);

    void Add<T>(string key, T value, DateTime absoluteExpiration);

    void Add<T>(string key, T value, CacheDependency dependencies);

    void Add<T>(string key, T value, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration);

    void Add<T>(string key, T value, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration,

    CacheItemUpdateCallback onUpdateCallback);

    void Add<T>(string key, T value, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration,

    CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback);

So how do we create an efficient caching solution without creating overloads for each supported options by a cache type.

The solution is to create a CacheOptions class that has a union of all options supported by all the cache types. So the example above can be rewritten as follows ...

interface ICache {

    void Add<T>(string key, T value, CacheOptions options);

class CacheOptions {

    public string FileName { get; set; }

    public DateTime AbsoluteExpiration { get; set; }

    public TimeSpan SlidingExpiration { get; set; }

    public CacheDependency Dependecy { get; set; }

    public CacheItemPriority priority { get; set; }

    public CacheItemUpdateCallback OnUpdateCallback { get; set; }

This does a few things for us ...

Simplify ICache interface, let each implementation work with the CacheOptions
Everytime we have a new Cache type, we don't have to modify the interface ICache, and thereby the other implementations
We can also initialize (with non-null values) some properties which are optional parameters. This results in cleaner code ...

Before ...

SomeCahce.Add("key", new object(), new CacheOptions() { AbsoluteExpiration = DateTime.MaxValue });

After ...

class CacheOptions {

    public CacheOptions() {

        // Default values

        AbsoluteExpiration = DateTime.MaxValue;

...

SomeCahce.Add("key", new object(), new CacheOptions());

Using Lambda Expressions for Events

noreply@blogger.com (Saket Porwal) — Wed, 29 Jul 2009 16:09:00 +0000

In the past, we created events using the following format …

public delegate void EventListener(object src, object context); public event EventListener SomeEvent; public void Init() { SomeEvent += OnSomeEvent; } public void OnSomeEvent(object src, object context) { }

With lambda expressions, we can do the following …

public event Action<object, object> SomeEvent; public void Init() { SomeEvent += (s,c) => {}; }

No doubt there are other ways to do it, but I find this simpler and more concise.

Interesting reading on Web Gardens

noreply@blogger.com (Saket Porwal) — Fri, 24 Jul 2009 21:05:00 +0000

If you want to learn more about Web Gardens, and gains and issue you might face, read these articles.

Available right-clicking an application pool and choosing Properties in the IIS Management snap-in.

One good learning from these articles was "Web gardening can be a good way to see if your application will be able to function in a Web farm scenario on multiple servers reasonably well"

Hotmail R.I.P. (1996-2009)

noreply@blogger.com (Saket Porwal) — Tue, 17 Mar 2009 01:12:00 +0000

Well not dead yet, but might as well be.

I have been using Hotmail since 1998, and have been using it till yesterday. As of today, I am proud to say that I am completely Hotmail-free. I am a pure GMail-er, all 100%.

There is no doubt that GMail has had far superior features as compared to Hotmail or Yahoo mail, two of the most popular free providers. So what took me so long to make the switch? Two things...

Old emails in Hotmail
Inability to mass update my email addresses without causing inconvenience, both to me and to others

I had previously posted (10 Indispensable 'GMail IMAP With Outlook' Hidden Features) a way to import files using GMail's IMAP service. But there was no way to import mails from Hotmail, well none until recently. Microsoft recently opened POP3 access to all Hotmail accounts (see gHacks).

So lets see what needs to be done for the move ...

Open Settings > Accounts
Click on 'Add a mail account you own'
Enter the following details...
Save

That's it, it should now import you Hotmail mail. Import one folder at a time and label them accordingly. Also GMail will let you reply to mail from Hotmail with either your Hotmail address or your GMail address. This ensures that people can continue sending mail to Hotmail or if you desire, to you GMail account from that point on.

Here are the settings in text form...

Incoming Server: pop3.live.com
Incoming Port: 995
SSL Encryption: yes

Not used for GMail, but rest of the settings ...

Outgoing Server: smtp.live.com
Outgoing port: 25 (use port 587 if the default port is not working)
Authentication: yes
TLS Or SSL: yes

Operator Overloading - Check for null value

noreply@blogger.com (Saket Porwal) — Fri, 13 Mar 2009 18:55:00 +0000

Height implements the operators, here is the current implantation of == operator …

public static bool operator ==(Height a, Height b)
{
return a.CMValue == b.CMValue;
}

#1 – What’s wrong with this code?

What happens if you want to do the following:
Height a = new Height(100);
Height b = null;
a == b

This will result in NullReferenceException … bad bad bad

Ok lets fix this …
public static bool operator ==(Height a, Height b)
{
if( a == null && b == null) return true;
if( a == null || b == null) return false;
return a.CMValue == b.CMValue;
}

#2 – What’s wrong with this code?

Do you see the recursiveness here?
a == null will call the same implementation, resulting in NullReferenceException … bad bad bad

Ok lets fix this…
public static bool operator ==(Height a, Height b)
{
object _a = (object)a, _b = (object)b;
if (_a == null && _b == null) return true;
if (_a == null || _b == null) return false;
return a.CMValue == b.CMValue;
}

By converting a and b to objects, we are using object’s implementation of the == operator, thus avoiding a recursive call.

Get ready for CERN: Talk on Particle Physics

noreply@blogger.com (Saket Porwal) — Tue, 09 Sep 2008 15:31:00 +0000

This is a follow up to the last video, to take a step further into particle physics. Get ready for the historic CERN supercollider's first beam on Sept 10th 2008. Watch Brian Cox explain the reason behind CERN.

The search for dark energy and dark matter

noreply@blogger.com (Saket Porwal) — Mon, 25 Aug 2008 18:06:00 +0000

Patricia Burchat's talk on TED: The search for dark energy and dark matter. Watch this if you are interested in astrophysics and the latest issues physicists are trying to solve.

Making the world a better place

noreply@blogger.com (Saket Porwal) — Thu, 14 Aug 2008 19:37:00 +0000

I have been a little busy last few months. Getting ready to launch a new site, details coming soon!

In the mean while, enjoy this one:

This is so typical of how most of us, me atleast, contribute to the global wealth ... sigh!

Randy Pausch Last Lecture: Achieving Your Childhood Dreams

noreply@blogger.com (Saket Porwal) — Fri, 25 Jul 2008 19:26:00 +0000

We spend our lives learning how to live, but it is mortality that teaches us what really truly matters.

Watch Prof. Randy Pausch present what are successful men made of. May his soul rest in peace.

Links from Week 27, 2008

noreply@blogger.com (Saket Porwal) — Mon, 07 Jul 2008 15:09:00 +0000

Coding > .Net

Config for release environment: ASP.NET Settings Schema

Coding > DB

Karl Seguin talks about Database Sharding
TOP n Per Group, Paging, and Common Table Expressions
NULLIF()
Partitions for Aggregate Functions
PARTITION and RANK
Tara Kizer's list on SQL Server jobs on production instances

Coding > Web

Coding Horror's post on Reducing Your Website's Bandwidth Usage
Techcrunch's post on Hacking The Facebook Platform For Data Portability

Finance

Roger Nusbaum shows how one can Follow Swensen's Yale Endowment Fund
Big Picture's post on Blue Chip losses so far

Miscellaneous

Grapeshisha has a good list of SOUKS IN DUBAI
The world's first moving skyscraper! in Dubai
Counting down the Top 10 TEDTalks ... must watch, must subscribe!
The BusinessWeek Best Seller List (books)

Links from Week 24, 2008

noreply@blogger.com (Saket Porwal) — Mon, 16 Jun 2008 20:16:00 +0000

Coding > .Net

MSDN's list of 101 LINQ Samples in C#
MSDN's list of LINQ to SQL Samples in VB (different from above)
Bilal Haider shows LEFT OUTER JOIN in LINQ To SQL
Wriju explains Paging Data in LINQ to SQL

Finance

Single Country Emerging Markets ETFs, ETNs and Closed-End Funds
iPath page on ETN Taxation
Excellent reference page of Currency ETFs and ETNs
Article compares currency ETNs and ETFs

Links from Week 23, 2008

noreply@blogger.com (Saket Porwal) — Mon, 09 Jun 2008 14:13:00 +0000

Coding > .Net

Marco De Sanctis presents L2S UnitOfWork pattern using ASP.Net Cache: Linq To Sql in real word Web applications
James present a technique to get JQuery IntelliSense in Visual Studio 2008
Dinesh Kulkarni explains Lifetime of a LINQ to SQL DataContext
Dave Ward explains using jQuery to call ASP.NET JSON Web Services and AJAX page methods
Muhammad presents details on datagrid editing using JQuery with jqModal
Maarten Balliauw teaches how to create a ASP.NET MVC GridView

Coding > Web

Noupe's resource list on JQuery Article on jQuery for designers explains Coda Slider Effect. Good screencast for jQuery, Firebug starters.

Finance

Mitch Tuchman explains Why the S&P SmallCap Index Consistently Beats the Russell 2000
Ray Hendon has a good article explaining Six Ways to Trade Foreign Currencies

Travel

NYT article on 31 Places to Go This Summer for less
Smashing Magazine article on 10 Places For Design Inspiration

Misc

Older post on Top 50 Blogger Powered Blogs

Links for Week 21, 2008

noreply@blogger.com (Saket Porwal) — Mon, 02 Jun 2008 12:30:00 +0000

Coding > .Net

Scott Hanselman's reference post on Libraries to Digg, Flickr, Facebook, YouTube, Twitter, Live Services, Google and other Web 2.0 APIs
David Hayden's must see screencasts on Unity as IoC Container: Unity Features and Getting started with Unity ASP.NET MVC
James Kovacs presents a good case for DI, IoC and Castle Windsor in his MSDN article: Loosen Up Tame Your Software Dependencies for More Flexible Apps

Coding > Web

Mashable has a good list of 16 Firefox Add-ons For Web Designers

Finance

Roger Nusbaum presents alternates for your ETF components in A Better Portfolio of ETFs

TDD: Test internal methods the correct way

noreply@blogger.com (Saket Porwal) — Tue, 27 May 2008 19:59:00 +0000

The aim: write a comprehensive suite of unit tests for a library we are creating.

Create a library project named Lib, which contains a class named StrExt, which contains a public method Tidy and an internal method IsBad. The implementation is as follows ...

namespace Lib
{
  public class StrExt
  {
   public string Tidy(string s)
   {
       if (IsBad(s) == false)
           return s.Trim();
       else
                return null;
   }

   internal bool IsBad(string s)
   {
       return s == null;
   }
 }
}

To test the above class, create a test project, call it Lib.Tests. In it, create the following test method to test the public method Tidy(string)...

    [TestMethod]
   public void Tidy_ReturnsCorrectValue()
   {
       string inStr = "test ";
       string expOutStr = "test";
       string actualOutStr = lib.Tidy(inStr);
       Assert.AreEqual(expOutStr, actualOutStr);
   }

This will work fine.

But what if we wanted to (and we should) test the internal method IsBad(string). Notice that the intellisense in the capture below does not display IsBad. This is obviously because the method IsBad, is declared internal to the Lib assembly and is therefore not visible to other assemblies such as Lib.Tests.

Writing tests for internal methods is a very common scenario. People often use convoluted techniques like Reflection etc to invoke the internal method. An easier and the correct solution is to use InternalsVisibleToAttribute as follows ...

using System.Runtime.CompilerServices;

[assembly: InternalsVisibleToAttribute("Lib.Tests")]

namespace Lib
{
  public class StrExt { ... /* No change in this class */ }
}

This makes the internal methods of the class visible to the named assembly. Now notice the intellisense ...

You can now test IsBad(string) in your test class as follows ...

using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace Lib
{
 [TestClass]
  public class Lib_UnitTests
  {
   private StrExt lib = new StrExt();

   [TestMethod]
   public void Tidy_ReturnsCorrectValue()
   {
       string inStr = "test ";
       string expOutStr = "test";
       string actualOutStr = lib.Tidy(inStr);
       Assert.AreEqual(expOutStr, actualOutStr);
   }

   [TestMethod]
   public void IsBad_ReturnsTrueForNullString()
   {
       string inStr = null;
       bool result = lib.IsBad(inStr);
       Assert.IsTrue(result);
   }
 }
}

Look ma, no reflection!

Links for Week 20, 2008

noreply@blogger.com (Saket Porwal) — Tue, 27 May 2008 05:05:00 +0000

Coding > .Net

Matt explains Using Post, Redirect, Get Pattern
MSDN article to help with HTTP request errors and solutions
New term POCO: Plain Old CLR Object

Coding > .Net > LINQ

Luca Bolognese's video on LINQ to SQL: Accessing Relational Data with Language Integrated Query, the single must see introductory video on the subject
Chris Rock's reference post on LINQ TO SQL Tutorials, Articles and Opinions
Benjamin Eidelman's post on the motives behind Unplugged LINQ to SQL Generator and the issues in using L2S for n-tired apps: First thoughts on Designing a LINQ-enabled Application Framework, and first view of
Benjamin Eidelman's excellent post on the problems and solutions in Implementing N-Tier with Linq to SQL
Rick Strahi's must-read post on Linq to SQL DataContext Lifetime Management, especially for n-tired apps

Extension Methods: Why you need to check for nulls?

noreply@blogger.com (Saket Porwal) — Mon, 26 May 2008 23:20:00 +0000

Extension methods is a good feature. For example, consider the following extension method ...

  public static string[] ToWordArray( this string str )
 {
     return str.Split( ' ' );
 }

Usage ...

    string s1 = "This is a sentence";
    string[] words = s1.ToWordArray();

Looking at the usage, it appears to be an instance method call. But this is misleading, when compiled, calls to 'ToWordArray' extension method are transformed by the compiler into static method calls. So the usage above is translated into ...

    string s1 = "This is a sentence";
    string[] words = string.ToWordArray(s1);

So, since this is not an instance call, the run-time will allow null reference to go through, resulting in NullReference exceptions. See the following example ...

    string s2 = null;
    string[] words = s2.ToWordArray(); // will result in exception

To avoid such issues, extension methods must test for null parameters. The above extension should be correctly implemented as below ...

  public static string[] ToWordArray( this string str )
 {
     if ( str == null )
         return null;
     else if ( str.Length == 0 )
         return new string[ 0 ];
     else // empty string has 0 words
            return str.Split( ' ' );
 }

WaitHandle

noreply@blogger.com (Saket Porwal) — Fri, 23 May 2008 20:13:00 +0000

Description

Used to synchronize threads' activities

Class Hierarchy

WaitHandle
- Mutex
- Semaphore
- EventWaitHandle
  - EventWaitHandle
    - AutoResetEvent
    - ManualResetEvent

Mutex: provides exclusive access to a resource. It uses more system resources than Monitor class, but can be marshaled across application domain boundaries, can be used with multiple waits, and can be used to synchronize threads in different processes

Semaphores: represent a named (system wide) or local semaphore, can be used to control access to a pool of resources

AutoResetEvent: provide exclusive access to a resource. When set, the event releases the waiting thread and immediately resets, blocking subsequent threads.

ManualResetEvent is useful when one thread must complete an activity before other threads can proceed.

Important Methods

WaitOne
WaitAny
WaitAll
SignalAndWait

SignalAndWait: A thread can signal an EventWaitHandle and then block on it, as an atomic operation, by calling this static method

References

MSDN page on WaitHandle

Links for Week 19, 2008

noreply@blogger.com (Saket Porwal) — Mon, 19 May 2008 05:30:00 +0000

Coding > .Net

Joe provides information on .NET 3.5 Enhancements Training Kit
Adrian has a good post on Unloadable plugins

Coding > SQL

Daniel Turini lists SQL Server DO's and DONT's
Basic Guidelines for Bulk Importing Data
Optimizing Bulk Import Performance
Boris Milrud provides a tip to Optimize Massive DELETE Operation

Finance

Don Dion's must-read article on Currency, Precious Metal and Futures ETFs: Don't Get Caught in the Tax Trap

Commodities, USA Chinese Economies, USD and Yuan - The Relation

noreply@blogger.com (Saket Porwal) — Wed, 14 May 2008 18:29:00 +0000

As of May 2008, USA is seeing a slow down, China is seeing higher inflation, Commodities are at all time highs. I tried to think logically through all this to see what some of the outcomes could be.

Chinese inflation at 8.5% yoy, near record highs
1. Increased production costs, higher export prices [6]
  1. Imported consumer goods get more expensive in USA [6]
    1. Additional upward pressure on USA inflation [12]
      1. US Fed eventually increase fed rates [18]
        
        USD rises [18]
        
        Commodities cool down [18]
  2. Less US demand for imported consumer goods , especially with high gas and food prices [12]
    1. Less production in China [18]
      1. Chinese economy slows down [24]
      2. Less demand for commodities from China [18]
        
        Commodities cool down [18]
2. Chinese Yuan rises [6]
  1. Exports become less profitable [6]
    1. Chinese economy slows down [12]
3. Chinese central bank controls inflation (this week boosted bank reserve requirements by 50 basis points to a record high of 16.5%) [12]
  1. Chinese economy slows down [18]

To conclude, over the next 2 years, I expect to see the following in chronological order:

Higher Chinese inflation

USA further slows down
Chinese Yuan rises

Chinese economy slows down

Commodities cool down
USD rises

Links for Week 18, 2008

noreply@blogger.com (Saket Porwal) — Sun, 11 May 2008 01:24:00 +0000

Coding > SQL

Another smart post by Jeff on GROUP BY ALL

Finance

Richard Shaw presents a good study on Major Asset Class 1, 3, 5, 10 & 15 Year Returns
Kirk's posts on Lazy Portfolios
Roger Nusbaum's posts on Lazy Portfolios
Paul Merriman provides some good tips on fund comparison in his: article
Jeff Merriman on how to create The perfect portfolio
World Interest Rates Table

ThreadAbortException in your C# .Net code?

noreply@blogger.com (Saket Porwal) — Sat, 10 May 2008 17:29:00 +0000

I was recently asked by someone to help debug a ThreadAbortException. Here's the simplified code ...

public class MyThread
{
 public void Run()
 {
     while( true )
     {
         try
            {
             lock( LockObj )
             {
                 Monitor.Wait( LockObj );
         }   }
         catch( Exception ex )
         {
             Console.WriteLine( ex.Message );
}   }   }   }

public void ThreadRunTest()
{
 MyThread thread = new MyThread();
 ThreadStart ts = new ThreadStart( thread.Run );
 Thread t = new Thread( ts );
 t.Start();
}

Running this results in the following exception message:

A first chance exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll

As the exception suggests, it seems MyThread is being aborted during execution. Running this sample code as a test case, you can reproduce the problem. Notice ThreadRunTest starts the thread, but does not wait for its completion. So when ThreadRunTest ends, all thread are forced to abort resulting in ThreadAbortException. So this should be a simple fix ...

public void ThreadRunTest()
{
MyThread thread = new MyThread();
ThreadStart ts = new ThreadStart( thread.Run );
Thread t = new Thread( ts );
t.Start();
t.Join();
}

Here are MSDN page on ThreadAbortException Class and Thread.Join Method

UPDATE: If you are using ThreadPool.QueueUserWorkItem, consider doing the following:

class MyClass
{
 static void Main()
 {
   AutoResetEvent autoEvent = new AutoResetEvent( false );
   ThreadPool.QueueUserWorkItem( new WaitCallback( WorkMethod ), autoEvent );
   autoEvent.WaitOne(); // Wait for background thread to end
 }

  static void WorkMethod( object stateInfo )
  {
    Console.WriteLine( "executing WorkMethod" );
    ( (AutoResetEvent)stateInfo ).Set(); // Signal that this thread is finished
  }
}

Links for Week 17, 2008

noreply@blogger.com (Saket Porwal) — Sun, 04 May 2008 04:45:00 +0000

Coding > .Net

Some introductory ASP.NET 3.5 Extensions Videos
The author explains how to enable pretty urls with Asp.Net MVC and IIS6
Scott Hanselman has a good post on OpenID and how to use in .Net applications
Scott Hanselman talks about Extensibility in .Net
Mark Dunn on Scaling and Persistence in Workflow Foundation on DNR TV

Coding > .Net > MVC

47 ASP.NET MVC Resources to Rock Your Development

Coding > .Net > TDD & Mocks

Phil Haack on TDD and Dependency Injection with ASP.NET MVC
Phil Haack presents a basic issue with Writing Unit Tests For Controller Actions and presents TDD techniques using Test Specific Subclasses and Rhino Mocks Extension Methods. Although the controller testing is much improved in the latest ASP.NET MVC Source Refresh Preview by returning ActionResult, these techniques can still be used elsewhere
Doga Oztuzun lists Free Training on ASP.NET MVC - ASP.NET Dynamic Data - Entity Framework - ADO.NET Data Services

Coding > .Net > IoC & DI

David Hayden screencasts on Unity IoC - Dependency Injection in ASP.NET MVC Framework
Scott Hanselman's List of .NET Dependency Injection Containers (IOC)

Coding > HTML

Antonio Lupetti has some really good techniques on Top-Down approach to simplify your CSS code
Useful jQuery: a Compilation of jQuery Utilities

Coding > HTML > CSS

Entrepreneurship

Rob Webb presents a great list of The best service providers for startups
Startup financing cycle in an picture ...

Finance

Roger Nusbaum talks about PBP BWV BEP: A Better ETF Solution for Call-Writing Funds
Phillip Lyon explains Why the Fed Should Leave Interest Rates Unchanged
New term Agflation

Finance > Commodities

Excellent reference post: Commodity ETFs and ETNs
A case for Commodities & introduction to Jim Rogers: Food Prices Will Only Rise: The Time to Buy is Now
A case for Commodity ETF slicing: Is Commodity ETF Slicing and Dicing Necessary?
Commodity funds by performance and composition: Commodity ETF Overview
A case for Agriculture: A Look At Agriculture. I tend to agree with author, I want my commodity portfolio to look like GCC
Jay Walker presents a case for Agriculture in Agricultural Commodities: Playing an Acknowledged Theme
Gaurav presents the contrarian case against Commodities Time to Short Commodities?

Noticeable

Did you hear about the SQL injection attacks, funny related strip ...

Free Trading: Zecco vs. Bank Of America vs. Wells Fargo - A Comparison

noreply@blogger.com (Saket Porwal) — Wed, 30 Apr 2008 19:27:00 +0000

I am trying to streamline my investments and one of the items on my agenda is to consolidate my banking accounts. Here's what I want from my new institute ...

Free/cheap basket or bucket trading
Umbrella institute for checking/saving/trading accounts
Support stocks/options/mutual funds/IRAs

I currently have account with Fidelity that comes close to what I need, but not close enough. So, here is an up-to-date (as of 4/30/2008) comparative chart on the institutes that meet one or more of these criteria...

	Zecco Trading	Bank of America	Wells Fargo
Free Trades Limit #	10/day, 40/month	30/month	100/year
Free Trades Minimum to Qualify $	2500	25000 (uninvested)	25000 (combined)
Stocks Penny Stocks $	0	0	Greater of $24.95 or 2.5% of principal
Stocks Max Margin Rate (on 4/30/2008) %	7.2	7.5	7.75
Stocks Broker Assisted $	19.99	42.5	25
Options Trade $ (contract $)	4.50 (0.50)	19.95 (1.50)	9.95 (1.00)
Options Broker Assisted $ (contract $)	19.99 (0.75)	39.95 (1.75)	34.95 (1.00)
Mutual Fund NTF #			800
Mutual Fund No Load Internet $	10	45 (minimum)	0
Mutual Fund No Load Broker Assisted $	19.99	45 (minimum)	25
IRA Annual Fees $	30	0	0
IRA Termination Fee $	30	75	50
Outgoing Account Transfer (ACAT) Fees $	50	75	50
Fees Web Site	Fee Schedule	Fee Schedule	Fee Schedule

Hope that helps.

Supporting admin and non-admin users in Windows XP/Vista applications

noreply@blogger.com (Saket Porwal) — Tue, 29 Apr 2008 17:07:00 +0000

Recently at work, in one of our windows based desktop application, we needed to support both admin and non-admin users in Windows Vista and Windows XP/2000

Here are some of my takeaways:

[For admin/XP] When an admin user executes an application, XP gives full admin rights to this application. With these privileges, there should be no problem reading / writing to any folder/registry.
[For admin/Vista] Unlike Windows XP, Windows Vista's UAC feature executes applications with standard privileges. So even if the user is logged in as an admin, the application has read-only access to the following common locations:
- C:\
- C:\Program Files
- C:\Windows
- HKLM
- 'All Users' profile or Application.CommonAppDataPath
[For non-admin/XP/Vista] Typically application data, which is common to all users (in a multi-user Windows desktop application), should be stored under 'All Users' profile or Application.CommonAppDataPath. This works great, except that a non-admin user has read-only permissions to this folder.

Point #1 is not really an issue. This is the easiest scenario to support.

For issues #2, a number of relevant solutions have been discussed in Dave's post "UnauthorizedAccessException writing to HKLM". But in case an application must store information in say HKLM or CommonAppDataPath, you can request UAC for elevated privileges. In order to do this, create a file called <projectname>.exe.manifest under the project root folder.

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
 <assemblyIdentity version="1.0.0.0" processorArchitecture="X86" name="Clean" type="win32"/>
 <trustInfo xmlns="urn:schemas-microsoft-com:asm.v3">
     <security>
         <requestedPrivileges>
                <requestedExecutionLevel level="requireAdministrator"/>
            </requestedPrivileges>
     </security>
 </trustInfo>
</assembly>

The following step is optional, but recommended since it adds the manifest file as an embedded resource in the final exe. Under "<project> > Properties > Build Events > Post Build Events", add the following line:

"$(DevEnvDir)..\..\SDK\v2.0\bin\mt.exe" -manifest "$(ProjectDir)$(TargetName).exe.manifest" –outputresource:"$(TargetDir)$(TargetFileName)";#1

For issue #3, we could not find a clean solution. We needed a way to provide write permissions to a folder for both the admin and the non-admin users. In our case, the application was to be installed in a lab environment by an admin and then used by non-admin users. In this type of setup, during installation, we moved the application data folder to say C:\ or D:\ and enabled write permissions for all users. This is not the most elegant solution, but I don't know of a better one. If there is a better solution, I am very interested to learn more, please add a comment below.

Microsoft MCTS .Net 3.5 Certification & Free Training Courses

noreply@blogger.com (Saket Porwal) — Thu, 03 Apr 2008 16:31:00 +0000

70-562 - Microsoft .NET Framework 3.5, ASP.NET Application Development (June 2008) Training:

Microsoft E-Learning - Collection 6463AE (June 2008)
Book - Programming Microsoft® ASP.NET 3.5 (February 2008)
Beta Exam 70-562 - See Gerry O'Brien's post on ASP.NET and ADO.NET Beta Exams (expires May 2008)

70-561 - Microsoft .NET Framework 3.5, ADO.NET Application Development Training:

Microsoft E-Learning - Collection 6464AE (April 2008)
Book - Microsoft .NET Framework 3.5 - ADO.NET (June 2008)
Book - Programming the Microsoft ADO.NET Entity Framework (December 2008)
Beta Exam 70-562 - See Gerry O'Brien's post on " (expires May 2008)

Please note that in order to get MCTS certification, you must first pass Microsoft .NET Framework 2.0—Application Development Foundation exam. If you are looking for additional .Net Framework 3.5 training, get some for free from Microsoft:

BTW, if you have doubts about the beta exams, here's a very informative quote from Gerry O'Brien's blog:

Passing the beta exam is equivalent to passing the live exam. Do you get certified? Only when all prerequisites are met. In other words, you must pass 70-536 and this exam to get an actual certification. This exam by itself does not award you the MCTS certification. For beta exams, you will not know if you pass or fail. The score report will indicate that you have failed but don't worry, the passing score has not been set so you haven't failed it, yet. Beta exam results are not made available until the exam is published live. We don't know the passing score until we finalize the questions after the beta. The difference between a beta and a live exam is that in the beta, you will typically take 100 or more questions whereas on the live, it can be 40 to 60 questions. Plan on a maximum of 4 hours for the beta exam.

Good Luck!