Dhinesh Paramasivam

2018-10-26T04:24:00.001-07:00

Cross Apply vs Outer Apply

CREATE TABLE #EmployeeDetails (

EmpId int PRIMARY KEY,

EmpFirstName VARCHAR(50),

EmpLastName VARCHAR(50),

Department VARCHAR(50),

DepartID INT

)

CREATE TABLE #EmpSalary (

EmpID INT,

EmpFullName VARCHAR(80),

EmpSalary INT,

EmpWorkingYears INT,

DepartID INT

)

　
Insert into #EmployeeDetails values(1001,'Kate', 'Thomas', 'IT',2)

Insert into #EmployeeDetails values(1002,'John', 'Wills', 'IT',2)

Insert into #EmployeeDetails values(1003,'Branda', 'Pat', 'Accounts',3)

Insert into #EmployeeDetails values(1004,'Sofia', 'Kaul', 'HR',1)

Insert into #EmployeeDetails values(1005,'Tim', 'Stouts', 'IT',2)

Insert into #EmployeeDetails values(1006,'Mick', 'Presto', 'Accounts',3)

Insert into #EmployeeDetails values(1007,'Steave', 'Berg', 'Trainee',null)

Insert into #EmpSalary values(1001, 'Kate Thomas', 35000, 3, 2)

Insert into #EmpSalary values(1002,'John Wills', 25000, 2, 2)

Insert into #EmpSalary values(1003, 'Branda Pat', 20000, 2, 3)

Insert into #EmpSalary values(1004, 'Sofia Kaul', 18000, 1, 1)

Insert into #EmpSalary values(1005, 'Tim Stouts', 25000, 2, 2)

Insert into #EmpSalary values(1006,'Mick Presto', 28000,3, 3)

Insert into #EmpSalary values(1007,'Petro johnson', 8000,1, null)

Insert into #EmpSalary values(1008,'Christie Pic', 6000,1, null)

--drop table #EmployeeDetails; drop table #EmpSalary

1.CROSS APPLY

The Cross Apply returns rows form the outer table (table on the left of the Apply operator)

that produces matching values from the table-valued function (which is on the right side of the operator).

The Cross Apply is equivalent to Inner Join, but it works with a table-valued function.

SELECT

e.EmpId,

e.EmpFirstName,

e.EmpLastName,

f.Salaryinc

FROM

#EmployeeDetails AS e

cross apply

(SELECT

EmpID, EmpFullName,

EmpSalary AS Salaryinc

FROM

#Empsalary
WHERE

DepartID = e.DepartID) f

2.OUTER APPLY
--The Outer Apply returns all the rows from the outer table (table on the left of the Apply operator),

--and rows that do not matches the condition from the table-valued function (which is on the right side of the operator), NULL values are displayed.

SELECT

e.EmpId,

e.EmpFirstName,

e.EmpLastName,

f.Salaryinc

FROM

#EmployeeDetails AS e

outer apply

(SELECT

EmpID, EmpFullName,

EmpSalary AS Salaryinc

FROM

#Empsalary
WHERE

DepartID = e.DepartID) f

MVC Page Life Cycle

2017-01-09T03:00:00.000-08:00

Xamarin Mobile App Development - Microsoft

2017-01-09T00:10:00.002-08:00

Xamarin Mobile App Development

Introduced by Microsoft to support Cross platform mobile app development
Installation Steps

https://developer.xamarin.com/guides/android/getting_started/installation/windows/#activate

It Supports both iOS & Android

MVC Interview Questions

2015-03-20T09:57:00.000-07:00

MVC - List of Questions

Reading these MVC interview questions does not mean you will go and clear MVC interviews. The purpose of this article is to quickly brush up your MVC knowledge before you go for MVC interviews. This article does not teach MVC, it’s a last minute revision sheet before going for MVC interviews.

If you want to learn MVC from scratch, start by reading Learn MVC ( Model view controller) step by step 7 days or you can also start with my step by step MVC (Model View Controller) video series from YouTube.

If you want to learn MVC 5 in a short time i.e. 2 days a.k.a 16 hours below is a video series for the same.

Need help to improve this article

I have tried my level best to cover what questions i have faced in MVC interviews. But i feel the below questions are not enough and in real MVC interview's much more is asked. If you can share your question in the comment below. I would love to incorporate them in this article so that others are benefited.
If your question is great and i like it i will ship you a free copy of my .NET interview question book only in India ( sorry i am not so rich for outside countries).

What is MVC (Model View Controller)?

MVC is an architectural pattern which separates the representation and user interaction. It’s divided into three broader sections, Model, View, and Controller. Below is how each one of them handles the task.

· The View is responsible for the look and feel.

· Model represents the real world object and provides data to the View.

· The Controller is responsible for taking the end user request and loading the appropriate Model and View.

Figure: MVC (Model view controller)

Explain MVC application life cycle?

There are six broader events which occur in MVC application life cycle below diagrams summarize it.

Image Courtesy: - http://www.dotnetinterviewquestions.in/article_explain-mvc-application-life-cycle_210.html

Any web application has two main execution steps first understanding the request and depending on the type of the request sending out appropriate response. MVC application life cycle is not different it has two main phases first creating the request object and second sending our response to the browser.

Creating the request object: -The request object creation has four major steps. Below is the detail explanation of the same.

Step 1 Fill route: - MVC requests are mapped to route tables which in turn specify which controller and action to be invoked. So if the request is the first request the first thing is to fill the route table with routes collection. This filling of route table happens in the global.asax file.

Step 2 Fetch route: - Depending on the URL sent “UrlRoutingModule” searches the route table to create “RouteData” object which has the details of which controller and action to invoke.

Step 3 Request context created: - The “RouteData” object is used to create the “RequestContext” object.

Step 4 Controller instance created: - This request object is sent to “MvcHandler” instance to create the controller class instance. Once the controller class object is created it calls the “Execute” method of the controller class.

Creating Response object: - This phase has two steps executing the action and finally sending the response as a result to the view.

Is MVC suitable for both Windows and Web applications?

The MVC architecture is suited for a web application than Windows. For Window applications, MVP, i.e., “Model View Presenter” is more applicable. If you are using WPF and Silverlight, MVVM is more suitable due to bindings.

What are the benefits of using MVC?

There are two big benefits of MVC:

· Separation of concerns is achieved as we are moving the code-behind to a separate class file. By moving the binding code to a separate class file we can reuse the code to a great extent.

· Automated UI testing is possible because now the behind code (UI interaction code) has moved to a simple .NET class. This gives us opportunity to write unit tests and automate manual testing.

Is MVC different from a three layered architecture?

MVC is an evolution of a three layered traditional architecture. Many components of the three layered architecture are part of MVC. So below is how the mapping goes:

Functionality	Three layered / tiered architecture	Model view controller architecture
Look and Feel	User interface	View
UI logic	User interface	Controller
Business logic /validations	Middle layer	Model
Request is first sent to	User interface	Controller
Accessing data	Data access layer	Data Access Layer

Figure: Three layered architecture

What is the latest version of MVC?

MVC 6 is the latest version which is also termed as ASP VNEXT.

What is the difference between each version of MVC 2, 3 , 4, 5 and 6?

MVC 6

ASP.NET MVC and Web API has been merged in to one.

Dependency injection is inbuilt and part of MVC.

Side by side - deploy the runtime and framework with your application

Everything packaged with NuGet, Including the .NET runtime itself.

New JSON based project structure.

No need to recompile for every change. Just hit save and refresh the browser.

Compilation done with the new Roslyn real-time compiler.

vNext is Open Source via the .NET Foundation and is taking public contributions.

vNext (and Rosyln) also runs on Mono, on both Mac and Linux today.

MVC 5

One ASP.NET

Attribute based routing

Asp.Net Identity

Bootstrap in the MVC template

Authentication Filters

Filter overrides

MVC 4

ASP.NET Web API

Refreshed and modernized default project templates

New mobile project template

Many new features to support mobile apps

Enhanced support for asynchronous methods

MVC 3

Razor

Readymade project templates

HTML 5 enabled templates

Support for Multiple View Engines

JavaScript and Ajax

Model Validation Improvements

MVC 2

Client-Side Validation

Templated Helpers

Areas

Asynchronous Controllers

Html.ValidationSummary Helper Method

DefaultValueAttribute in Action-Method Parameters

Binding Binary Data with Model Binders

DataAnnotations Attributes

Model-Validator Providers

New RequireHttpsAttribute Action Filter

Templated Helpers

Display Model-Level Errors

What are HTML helpers in MVC?

HTML helpers help you to render HTML controls in the view. For instance if you want to display a HTML textbox on the view , below is the HTML helper code.

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<%= Html.TextBox("LastName") %>

For checkbox below is the HTML helper code. In this way we have HTML helper methods for every HTML control that exists.

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<%= Html.CheckBox("Married") %>

What is the difference between “HTML.TextBox” vs “HTML.TextBoxFor”?

Both of them provide the same HTML output, “HTML.TextBoxFor” is strongly typed while “HTML.TextBox” isn’t. Below is a simple HTML code which just creates a simple textbox with “CustomerCode” as name.

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Html.TextBox("CustomerCode")

Below is “Html.TextBoxFor” code which creates HTML textbox using the property name ‘CustomerCode” from object “m”.

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Html.TextBoxFor(m => m.CustomerCode)

In the same way we have for other HTML controls like for checkbox we have “Html.CheckBox” and “Html.CheckBoxFor”.

What is routing in MVC?

Routing helps you to define a URL structure and map the URL with the controller.

For instance let’s say we want that when a user types “http://localhost/View/ViewCustomer/”, it goes to the “Customer” Controller and invokes the DisplayCustomer action. This is defined by adding an entry in to theroutes collection using the maproute function. Below is the underlined code which shows how the URL structure and mapping with controller and action is defined.

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routes.MapRoute(

"View", // Route name

"View/ViewCustomer/{id}", // URL with parameters

new { controller = "Customer", action = "DisplayCustomer",

id = UrlParameter.Optional }); // Parameter defaults

Where is the route mapping code written?

The route mapping code is written in "RouteConfig.cs" file and registered using "global.asax" application start event.

Can we map multiple URL’s to the same action?

Yes, you can, you just need to make two entries with different key names and specify the same controller and action.

Explain attribute based routing in MVC?

This is a feature introduced in MVC 5. By using the "Route" attribute we can define the URL structure. For example in the below code we have decorated the "GotoAbout" action with the route attribute. The route attribute says that the "GotoAbout" can be invoked using the URL structure "Users/about".

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public class HomeController : Controller

{

[Route("Users/about")]

public ActionResult GotoAbout()

{

return View();

}

What is the advantage of defining route structures in the code?

Most of the time developers code in the action methods. Developers can see the URL structure right upfront rather than going to the “routeconfig.cs” and see the lengthy codes. For instance in the below code the developer can see right upfront that the “GotoAbout” action can be invoked by four different URL structure.

This is much user friendly as compared to scrolling through the “routeconfig.cs” file and going through the length line of code to figure out which URL structure is mapped to which action.

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public class HomeController : Controller

{

[Route("Users/about")]

[Route("Users/WhoareWe")]

[Route("Users/OurTeam")]

[Route("Users/aboutCompany")]

public ActionResult GotoAbout()

{

return View();

}

How can we navigate from one view to another using a hyperlink?

By using the ActionLink method as shown in the below code. The below code will create a simple URL which helps to navigate to the “Home” controller and invoke the GotoHome action.

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<%= Html.ActionLink("Home","Gotohome") %>

How can we restrict MVC actions to be invoked only by GET or POST?

We can decorate the MVC action with the HttpGet or HttpPost attribute to restrict the type of HTTP calls. For instance you can see in the below code snippet the DisplayCustomer action can only be invoked by HttpGet. If we try to make HTTP POST on DisplayCustomer, it will throw an error.

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[HttpGet]

public ViewResult DisplayCustomer(int id)

{

Customer objCustomer = Customers[id];

return View("DisplayCustomer",objCustomer);

}

How can we maintain sessions in MVC?

Sessions can be maintained in MVC by three ways: tempdata, viewdata, and viewbag.

What is the difference between tempdata, viewdata, and viewbag?

Figure: Difference between tempdata, viewdata, and viewbag

· Temp data - Helps to maintain data when you move from one controller to another controller or from one action to another action. In other words when you redirect, tempdata helps to maintain data between those redirects. It internally uses session variables.

· View data - Helps to maintain data when you move from controller to view.

· View Bag - It’s a dynamic wrapper around view data. When you use Viewbag type, casting is not required. It uses the dynamic keyword internally.

Figure: dynamic keyword

· Session variables - By using session variables we can maintain data from any entity to any entity.

· Hidden fields and HTML controls - Helps to maintain data from UI to controller only. So you can send data from HTML controls or hidden fields to the controller using POST or GET HTTP methods.

Below is a summary table which shows the different mechanisms for persistence.

Maintains data between	ViewData/ViewBag	TempData	Hidden fields	Session
Controller to Controller	No	Yes	No	Yes
Controller to View	Yes	No	No	Yes
View to Controller	No	No	Yes	Yes

What is difference between TempData and ViewData ?

“TempData” maintains data for the complete request while “ViewData” maintains data only from Controller to the view.

Does “TempData” preserve data in the next request also?

“TempData” is available through out for the current request and in the subsequent request it’s available depending on whether “TempData” is read or not.

So if “TempData” is once read it will not be available in the subsequent request.

What is the use of Keep and Peek in “TempData”?

Once “TempData” is read in the current request it’s not available in the subsequent request. If we want “TempData” to be read and also available in the subsequent request then after reading we need to call “Keep” method as shown in the code below.

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@TempData[“MyData”];

TempData.Keep(“MyData”);

The more shortcut way of achieving the same is by using “Peek”. This function helps to read as well advices MVC to maintain “TempData” for the subsequent request.

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string str = TempData.Peek("Td").ToString();

If you want to read more in detail you can read from this detailed blog on MVC Peek and Keep.

What are partial views in MVC?

Partial view is a reusable view (like a user control) which can be embedded inside other view. For example let’s say all your pages of your site have a standard structure with left menu, header, and footer as shown in the image below.

Figure: Partial views in MVC

For every page you would like to reuse the left menu, header, and footer controls. So you can go and create partial views for each of these items and then you call that partial view in the main view.

How did you create a partial view and consume it?

When you add a view to your project you need to check the “Create partial view” check box.

Figure: Create partial view

Once the partial view is created you can then call the partial view in the main view using theHtml.RenderPartial method as shown in the below code snippet:

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<body>

<div>

<% Html.RenderPartial("MyView"); %>

</div>

</body>

How can we do validations in MVC?

One of the easiest ways of doing validation in MVC is by using data annotations. Data annotations are nothing but attributes which can be applied on model properties. For example, in the below code snippet we have a simple Customer class with a property customercode.

This CustomerCode property is tagged with a Required data annotation attribute. In other words if this model is not provided customer code, it will not accept it.

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public class Customer

{

[Required(ErrorMessage="Customer code is required")]

public string CustomerCode

{

set;

get;

}

In order to display the validation error message we need to use the ValidateMessageFor method which belongs to the Html helper class.

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<% using (Html.BeginForm("PostCustomer", "Home", FormMethod.Post))

{ %>

<%=Html.TextBoxFor(m => m.CustomerCode)%>

<%=Html.ValidationMessageFor(m => m.CustomerCode)%>

<%}%>

Later in the controller we can check if the model is proper or not by using the ModelState.IsValid property and accordingly we can take actions.

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public ActionResult PostCustomer(Customer obj)

{

if (ModelState.IsValid)

{

obj.Save();

return View("Thanks");

}

else

{

return View("Customer");

}

Below is a simple view of how the error message is displayed on the view.

Figure: Validations in MVC

Can we display all errors in one go?

Yes, we can; use the ValidationSummary method from the Html helper class.

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<%= Html.ValidationSummary() %>

What are the other data annotation attributes for validation in MVC?

If you want to check string length, you can use StringLength.

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[StringLength(160)]

public string FirstName { get; set; }

In case you want to use a regular expression, you can use the RegularExpression attribute.

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[RegularExpression(@"[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}")]public string Email { get; set; }

If you want to check whether the numbers are in range, you can use the Range attribute.

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[Range(10,25)]public int Age { get; set; }

Sometimes you would like to compare the value of one field with another field, we can use the Compareattribute.

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public string Password { get; set; }[Compare("Password")]public string ConfirmPass { get; set; }

In case you want to get a particular error message , you can use the Errors collection.

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var ErrMessage = ModelState["Email"].Errors[0].ErrorMessage;

If you have created the model object yourself you can explicitly call TryUpdateModel in your controller to check if the object is valid or not.

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TryUpdateModel(NewCustomer);

In case you want add errors in the controller you can use the AddModelError function.

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ModelState.AddModelError("FirstName", "This is my server-side error.");

How can we enable data annotation validation on client side?

It’s a two-step process: first reference the necessary jQuery files.

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The second step is to call the EnableClientValidation method.

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<% Html.EnableClientValidation(); %>

What is Razor in MVC?

It’s a light weight view engine. Till MVC we had only one view type, i.e., ASPX. Razor was introduced in MVC 3.

Why Razor when we already have ASPX?

Razor is clean, lightweight, and syntaxes are easy as compared to ASPX. For example, in ASPX to display simple time, we need to write:

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<%=DateTime.Now%>

In Razor, it’s just one line of code:

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@DateTime.Now

So which is a better fit, Razor or ASPX?

As per Microsoft, Razor is more preferred because it’s light weight and has simple syntaxes.

How can you do authentication and authorization in MVC?

You can use Windows or Forms authentication for MVC.

How to implement Windows authentication for MVC?

For Windows authentication you need to modify the web.config file and set the authentication mode to Windows.

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</authorization>

Then in the controller or on the action, you can use the Authorize attribute which specifies which users have access to these controllers and actions. Below is the code snippet for that. Now only the users specified in the controller and action can access it.

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[Authorize(Users= @"WIN-3LI600MWLQN\Administrator")]

public class StartController : Controller

{

// GET: /Start/

[Authorize(Users = @"WIN-3LI600MWLQN\Administrator")]

public ActionResult Index()

{

return View("MyView");

}

How do you implement Forms authentication in MVC?

Forms authentication is implemented the same way as in ASP.NET. The first step is to set the authentication mode equal to Forms. The loginUrl points to a controller here rather than a page.

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</authentication>

We also need to create a controller where we will check if the user is proper or not. If the user is proper we will set the cookie value.

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public ActionResult Login()

{

if ((Request.Form["txtUserName"] == "Shiv") &&

(Request.Form["txtPassword"] == "Shiv@123"))

{

FormsAuthentication.SetAuthCookie("Shiv",true);

return View("About");

}

else

{

return View("Index");

}

All the other actions need to be attributed with the Authorize attribute so that any unauthorized user making a call to these controllers will be redirected to the controller (in this case the controller is “Login”) which will do the authentication.

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[Authorize]

PublicActionResult Default()

{

return View();

}

[Authorize]

publicActionResult About()

{

return View();

}

How to implement AJAX in MVC?

You can implement AJAX in two ways in MVC:

· AJAX libraries

· jQuery

Below is a simple sample of how to implement AJAX by using the “AJAX” helper library. In the below code you can see we have a simple form which is created by using the Ajax.BeginForm syntax. This form calls a controller action called getCustomer. So now the submit action click will be an asynchronous AJAX call.

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Please do read this blog which has detailed steps of how model binders can be created using “IModelBinder” interface: - Explain MVC model Binders?

What is the difference between .Net Remoting and Asp.Net Web Services?

2012-02-23T04:36:00.001-08:00

ASP.NET Web Services Can be accessed only over HTTP but .Net Remoting Can be accessed over various protocols like TCP, HTTP, SMTP etc.

Web Services are based on stateless service architecture but .Net Remoting support for both stateful and stateless environment.

Web Services support heterogeneous environments means interoperability across platforms but .Net remoting requires .Net on both server and client end.

.NET Remoting provides the fast communication than Web Services when we use the TCP channel and the binary formatter.

Web services support only the objects that can be serialized but .NET Remoting can provide support to all objects that inherit MarshalByRefObject.

Web Services are reliable than .Net remoting because Web services are always hosted in IIS.

Web Services are ease to create and deploy but .Net remoting is bit complex to program.

How to Use IDisposable Pattern

2010-12-09T00:26:00.000-08:00

public class DisposeObject : IDisposable
{
#region Members

private bool _disposed = false;

#endregion

#region IDisposable Members

~DisposeObject()
{
Dispose(false);
}

///

/// Dispose the current object
///

public void Dispose()
{
Dispose(true);
}

private void Dispose(bool disposing)
{
if (!_disposed)
{
if (disposing)
{
// clean up resources

CleanUp();

// The object will be cleaned up only if the method
// gets true - we are in the Dispose method.
// Therefore, you should call GC.SupressFinalize to
// take this object off the finalization queue
// and prevent finalization code for this object
// from executing a second time.
// Taken from MSDN.
GC.SuppressFinalize(this);
}
// dispose occurred
_disposed = true;
}
}

private void CleanUp()
{
// put here the code to dispose all managed
// and unmanaged resources
}

#endregion
}

Events and Delegates

2010-03-11T02:17:00.001-08:00

The very basic Delegate

An interesting and useful property of a delegate is that it does not know or care about the class of the object that it references. Any object will do; all that matters is that the method's argument types and return type match the delegate's. This makes delegates perfectly suited for "anonymous" invocation.

The signature of a single cast delegate is shown below:

delegate result-type identifier ([parameters]);

where:

result-type: The result type, which matches the return type of the function.
identifier: The delegate name.
parameters: The Parameters, that the function takes.
Examples:

public delegate void SimpleDelegate ()

This declaration defines a delegate named SimpleDelegate, which will encapsulate any method that takes
no parameters and returns no value.

public delegate int ButtonClickHandler (object obj1, object obj2)

This declaration defines a delegate named ButtonClickHandler, which will encapsulate any method that takes
two objects as parameters and returns an int.

A delegate will allow us to specify what the function we'll be calling looks like without having to specify which function to call. The declaration for a delegate looks just like the declaration for a function, except that in this case, we're declaring the signature of functions that this delegate can reference.

There are three steps in defining and using delegates:

Declaration
Instantiation
Invocation
A very basic example (SimpleDelegate1.cs):

using System;

namespace Akadia.BasicDelegate
{
// Declaration
public delegate void SimpleDelegate();

class TestDelegate
{
public static void MyFunc()
{
Console.WriteLine("I was called by delegate ...");
}

public static void Main()
{
// Instantiation
SimpleDelegate simpleDelegate = new SimpleDelegate(MyFunc);

// Invocation
simpleDelegate();
}
}
}

Compile an test:

# csc SimpleDelegate1.cs
# SimpleDelegate1.exe
I was called by delegate ...

Calling Static Functions

For our next, more advanced example (SimpleDelegate2.cs), declares a delegate that takes a single string parameter and has no return type:

using System;

namespace Akadia.SimpleDelegate
{
// Delegate Specification
public class MyClass
{
// Declare a delegate that takes a single string parameter
// and has no return type.
public delegate void LogHandler(string message);

// The use of the delegate is just like calling a function directly,
// though we need to add a check to see if the delegate is null
// (that is, not pointing to a function) before calling the function.
public void Process(LogHandler logHandler)
{
if (logHandler != null)
{
logHandler("Process() begin");
}

if (logHandler != null)
{
logHandler ("Process() end");
}
}
}

// Test Application to use the defined Delegate
public class TestApplication
{
// Static Function: To which is used in the Delegate. To call the Process()
// function, we need to declare a logging function: Logger() that matches
// the signature of the delegate.
static void Logger(string s)
{
Console.WriteLine(s);
}

static void Main(string[] args)
{
MyClass myClass = new MyClass();

// Crate an instance of the delegate, pointing to the logging function.
// This delegate will then be passed to the Process() function.
MyClass.LogHandler myLogger = new MyClass.LogHandler(Logger);
myClass.Process(myLogger);
}
}
}

Compile an test:

# csc SimpleDelegate2.cs
# SimpleDelegate2.exe
Process() begin
Process() end

Events and Delegates

2010-03-11T02:01:00.000-08:00

Simple Event
Let's modify our logging example from above to use an event rather than a delegate:
using System;
using System.IO;

namespace Akadia.SimpleEvent
{
/* ========= Publisher of the Event ============== */
public class MyClass
{
// Define a delegate named LogHandler, which will encapsulate
// any method that takes a string as the parameter and returns no value
public delegate void LogHandler(string message);

// Define an Event based on the above Delegate
public event LogHandler Log;

// Instead of having the Process() function take a delegate
// as a parameter, we've declared a Log event. Call the Event,
// using the OnXXXX Method, where XXXX is the name of the Event.
public void Process()
{
OnLog("Process() begin");
OnLog("Process() end");
}

// By Default, create an OnXXXX Method, to call the Event
protected void OnLog(string message)
{
if (Log != null)
{
Log(message);
}
}
}

// The FileLogger class merely encapsulates the file I/O
public class FileLogger
{
FileStream fileStream;
StreamWriter streamWriter;

// Constructor
public FileLogger(string filename)
{
fileStream = new FileStream(filename, FileMode.Create);
streamWriter = new StreamWriter(fileStream);
}

// Member Function which is used in the Delegate
public void Logger(string s)
{
streamWriter.WriteLine(s);
}

public void Close()
{
streamWriter.Close();
fileStream.Close();
}
}

/* ========= Subscriber of the Event ============== */
// It's now easier and cleaner to merely add instances
// of the delegate to the event, instead of having to
// manage things ourselves
public class TestApplication
{
static void Logger(string s)
{
Console.WriteLine(s);
}

static void Main(string[] args)
{
FileLogger fl = new FileLogger("process.log");
MyClass myClass = new MyClass();

// Subscribe the Functions Logger and fl.Logger
myClass.Log += new MyClass.LogHandler(Logger);
myClass.Log += new MyClass.LogHandler(fl.Logger);

// The Event will now be triggered in the Process() Method
myClass.Process();

fl.Close();
}
}
}
Compile an test:
# csc SimpleEvent.cs
# SimpleEvent.exe
Process() begin
Process() end
# cat process.log
Process() begin
Process() end

Transact-SQL Optimization Tips.

2010-03-01T05:15:00.000-08:00

Here are fourteen little known tips that you can use to ensure your Transact-SQL queries are performing in the most efficient manner possible.

1. Try to restrict the queries result set by using the WHERE clause.
This can result in a performance benefit, as SQL Server will return to the client only particular rows, not all rows from the table(s). This can reduce network traffic and boost the overall performance of the query.
2. Try to restrict the queries result set by returning only the particular columns from the table, not all the table's columns.
This can result in a performance benefit as well, because SQL Server will return to the client only particular columns, not all the table's columns. This can reduce network traffic and boost the overall performance of the query.
3. Use views and stored procedures instead of heavy-duty queries.
This can reduce network traffic as your client will send to the server only stored procedures or view name (perhaps with some parameters) instead of large heavy-duty queries text. This can be used to facilitate permission management also, because you can restrict user access to table columns they should not see.
4. Whenever possible, try to avoid using SQL Server cursors.
SQL Server cursors can result in some performance degradation in comparison with select statements. Try to use correlated subquery or derived tables, if you need to perform row-by-row operations.
5. If you need to return the total table's row count, you can use an alternative way instead of the SELECT COUNT(*) statement.
Because the SELECT COUNT(*) statement makes a full table scan to return the total table's row count, it can take an extremely long time for large tables. There is another way to determine the total row count in a table. In this case, you can use the sysindexes system table. There is a ROWS column in the sysindexes table. This column contains the total row count for each table in your database. So, you can use the following select statement instead of SELECT COUNT(*):
SELECT rows FROM sysindexes WHERE id = OBJECT_ID('table_name') AND in did < href="http://www.mssqlcity.com/Articles/KnowHow/RowCount.htm"> Alternative way to get the table's row count.
6. Try to use constraints instead of triggers, whenever possible.
Constraints are much more efficient than triggers and can boost performance. So, whenever possible, you should use constraints instead of triggers.
7. Use table variables instead of temporary tables.
Table variables require fewer locking and logging resources than temporary tables, so table variables should be used whenever possible. The table variables are available in SQL Server 2000 only.
8. Try to avoid the HAVING clause, whenever possible.
The HAVING clause is used to restrict the result set returned by the GROUP BY clause. When you use GROUP BY with the HAVING clause, the GROUP BY clause divides the rows into sets of grouped rows and aggregates their values, and then the HAVING clause eliminates undesired aggregated groups. In many cases, you can write your select statement so that they will contain only WHERE and GROUP BY clauses without the HAVING clause. This can improve the performance of your query.
9. Whenever possible, try to avoid using the DISTINCT clause.
Because using the DISTINCT clause will result in some performance degradation, you should use this clause only when it is absolutely necessary.
10. Include SET NOCOUNT ON statement into your stored procedures to stop the message indicating the number of rows affected by a T-SQL statement.
This can reduce network traffic, as your client will not receive the message indicating the number of rows affected by a T-SQL statement.
11. Use select statements with the TOP keyword or the SET ROWCOUNT statement if you need to return only the first n rows.
This can improve performance of your queries, as a smaller result set will be returned. This can also reduce the traffic between the server and the clients.
12. Use the FAST number_rows table hint if you need to quickly return 'number_rows' rows.
You can quickly get the n rows and can work with them when the query continues execution and produces its full result set.
13. Try to use UNION ALL statement instead of UNION, whenever possible.
The UNION ALL statement is much faster than UNION, because UNION ALL statement does not look for duplicate rows, while the UNION statement does look for duplicate rows, whether they exist or not.
14. Do not use optimizer hints in your queries.
Because the SQL Server query optimizer is very clever, it is highly unlikely that you can optimize your query by using optimizer hints; more often than not, this will hurt performance.

Difference b/w UDFs and Stored Procedures

2010-02-26T01:25:00.000-08:00

1>Procedure can return zero or n values whereas function can return one value which is mandatory.
2>Procedures can have input,output parameters for it whereas functions can have only input parameters.
3>Procedure allow select as well as DML statement in it whereas function allow only select statement in it.
4>Functions can be called from procedure whereas procedures cannot be called from function.
5>Exception can be handled by try-catch block in a procedure whereas try-catch block cannot be used in a function.
6>We can go for transaction management in procedure whereas we can't go in function.
7>Procedures can not be utilized in a select statement whereas function can be embedded in a select statement.

Static Constructor limitations

2010-02-03T05:31:00.000-08:00

Example:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
C Obj = new C();
C.C1();
Console.ReadKey();
}
}

public static class DHINESH
{
static DHINESH()
{
DHINESH1();
}

static void DHINESH1()
{

}
}

public class A
{
public A()
{
Console.WriteLine("This is A");
}

static A()
{
Console.WriteLine("This is static A");
}
}

public class B : A
{
public B()
{
Console.WriteLine("This is B");
}

static B()
{
Console.WriteLine("This is static B");
}
}

public class C : B
{
public C()
{
Console.WriteLine("This is C");
}

static C()
{
Console.WriteLine("This is static C");
}

public static void C1()
{

}
}
}

Result:
-->When we instantiate a Class like this C Obj = new C();

The output is :

This is static C
This is static B
This is static A
This is A
This is B
This is C

-->When we instantiate a Class like this

C Obj = new C();
C Obj1 = new C();

The output is :

This is static C
This is static B
This is static A
This is A
This is B
This is C
This is A
This is B
This is C

-->When we call a static method like this C.C1();

The output is:

This is static C

Limitations of Static constructor:

1. We cannot specify access modifier.
2. We cannot use any parameter.
3. Static constructor will be executing only once and also very first instance of the class.
4. When any static method of the class is being called the static constructor will be executing at first call itself.
5.We can use only static members or variables inside the static constructor.

How to restrict back button in asp.net.

2010-02-02T07:11:00.000-08:00

We have come across the problem while clicking on the back button in the browser.

we shouldn't load the page again when we click on the back button.

Below code it will hide the back button. This is also one of the security leavl have to

follow in the transaction pages.

Response.Buffer = true;
Response.CacheControl = "no-cache";
Response.Cache.SetNoStore();
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetExpires(DateTime.Now.AddDays(-1));

Design Patterns

2010-02-02T01:49:00.000-08:00

Creational Patterns:

Abstract Factory: Creates an instance of several families of classes
Builder: Separates object construction from its representation
Factory Method: Creates an instance of several derived classes
Prototype: A fully initialized instance to be copied or cloned
Singleton: A class of which only a single instance can exist

Structural Patterns:

Adapter: Match interfaces of different classes
Bridge: Separates an object’s interface from its implementation
Composite: A tree structure of simple and composite objects
Decorator: Add responsibilities to objects dynamically
Facade: A single class that represents an entire subsystem
Flyweight: A fine-grained instance used for efficient sharing
Proxy: An object representing another object

Behavioral Patterns:

Chain of Resp: A way of passing a request between a chain of objects
Command: Encapsulate a command request as an object
Interpreter: A way to include language elements in a program
Iterator: Sequentially access the elements of a collection
Mediator: Defines simplified communication between classes
Memento: Capture and restore an object's internal state
Observer: A way of notifying change to a number of classes
State: Alter an object's behavior when its state changes
Strategy: Encapsulates an algorithm inside a class
Template: Method Defer the exact steps of an algorithm to a subclass
Visitor: Defines a new operation to a class without change

Sys.StringBuilder Class in Ajax

2010-01-04T22:38:00.000-08:00

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Ajax_StringBuilder.aspx.cs" Inherits="Ajax_StringBuilder" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager runat="server" ID="ScriptManager1">
</asp:ScriptManager>

<script type="text/javascript">
function buildAString(title){
var headTagStart = "<head>";
var headTagEnd = "</head>";
var titleTagStart = "<title>";
var titleTagEnd = "</title>";

var sb = new Sys.StringBuilder(this._headTagStart);
Sys.Application.add_load(load);
sb.append(titleTagEnd);
sb.append(title);
sb.append(titleTagEnd);
sb.append(headTagEnd);
// Displays: "The result: <head><title>A Title</title></head>"
//alert("The result" + sb.toString());
}

var title = "A Title";
buildAString(title);
function load()
{

}
</script>
<asp:TextBox ID="txtTest" runat="server"></asp:TextBox>

<%
Application.Add("Counter", 1);
Application["Counter"] = (int)Application["Counter"] + 1;
%>
</form>
</body>
</html>

ICallbackEventHandler Sample

2009-12-14T03:14:00.000-08:00

.ASPX Page

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="CallBackEventValidationServer.aspx.cs" Inherits="CallBackEventHandler_CallBackEventValidationServer" %>

html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<title>Untitled Page<title>

function ReceiveServerData(rValue)

{

alert(rValue);

}

<body>

<asp:ScriptManager ID="sm" runat="server">asp:ScriptManager>

<div>

Name: <input type="text" id="Name" runat="server" />

Address: <input type="text" id="Address" runat="server" />

<div>

<form>

<body>

<html>

.CS Page

using System;

using System.Collections;

using System.Configuration;

using System.Data;

using System.Linq;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.HtmlControls;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Xml.Linq;

public partial class CallBackEventHandler_CallBackEventValidationServer : System.Web.UI.Page,ICallbackEventHandler

{

protected string returnValue = string.Empty;

protected void Page_Load(object sender, EventArgs e)

{

ClientScriptManager cm = Page.ClientScript;

String cbReference = cm.GetCallbackEventReference(this, "arg", "ReceiveServerData", "");

String callbackScript = "function CallServer(arg, context) {" + cbReference + "; }";

cm.RegisterClientScriptBlock(this.GetType(), "CallServer", callbackScript, true);

}

#region ICallbackEventHandler Members

public string GetCallbackResult()

{

return returnValue;

}

public void RaiseCallbackEvent(string eventArgument)

{

try

{

Page.ClientScript.ValidateEvent("SUBMIT");

// Callback logic goes here.

if (Name.Value == string.Empty)

{

returnValue += "* Please fill the value for Name \n";

}

if (Address.Value == string.Empty)

{

returnValue += "* Please fill the value for Address \n";

}

catch

{

// Failed callback validation logic.

}

#endregion

protected override void Render(HtmlTextWriter writer)

{

Page.ClientScript.RegisterForEventValidation("SUBMIT");

base.Render(writer);

}

Controls that Are Not Compatible with UpdatePanel Controls

2009-12-14T01:25:00.000-08:00

The following ASP.NET controls are not compatible with partial-page updates, and are therefore not supported inside an UpdatePanel control:

TreeView and Menu controls.
Web Parts controls. For more information, see ASP.NET Web Parts Pages.
FileUpload controls when they are used to upload files as part of an asynchronous postback.
GridView and DetailsView controls when their EnableSortingAndPagingCallbacks property is set to true. The default is false.
Login, PasswordRecovery, ChangePassword, and CreateUserWizard controls whose contents have not been converted to editable templates.
The Substitution control.
Validation controls, which includes the BaseCompareValidator, BaseValidator, CompareValidator, CustomValidator, RangeValidator, RegularExpressionValidator, RequiredFieldValidator, and ValidationSummary control.

C#.Net and Vb.Net Keyword Differences

2009-12-08T05:31:00.001-08:00

Imports System

Namespace Hello
Class HelloWorld
Overloads Shared Sub Main(ByVal args() As String)
Dim name As String = "VB.NET"

'See if an argument was passed from the command line
If args.Length = 1 Then name = args(0)

Console.WriteLine("Hello, " & name & "!")
End Sub
End Class
End Namespace

using System;

namespace Hello {
public class HelloWorld {
public static void Main(string[] args) {
string name = "C#";

// See if an argument was passed from the command line
if (args.Length == 1)
name = args[0];

Console.WriteLine("Hello, " + name + "!");
}
}
}

' Single line only
REM Single line only
'''

XML comments

// Single line
/* Multiple
line */
///

XML comments on single line

/**

XML comments on multiple lines

Value Types
Boolean
Byte, SByte
Char
Short, UShort, Integer, UInteger, Long, ULong
Single, Double
Decimal
Date

Reference Types
Object
String

Initializing
Dim correct As Boolean = True
Dim b As Byte = &H2A 'hex
Dim o As Byte = &O52 'octal
Dim person As Object = Nothing
Dim name As String = "Dwight"
Dim grade As Char = "B"c
Dim today As Date = #12/31/2007 12:15:00 PM#
Dim amount As Decimal = 35.99@
Dim gpa As Single = 2.9!
Dim pi As Double = 3.14159265
Dim lTotal As Long = 123456L
Dim sTotal As Short = 123S
Dim usTotal As UShort = 123US
Dim uiTotal As UInteger = 123UI
Dim ulTotal As ULong = 123UL

Type Information
Dim x As Integer
Console.WriteLine(x.GetType()) ' Prints System.Int32
Console.WriteLine(GetType(Integer)) ' Prints System.Int32
Console.WriteLine(TypeName(x)) ' Prints Integer

Type Conversion
Dim d As Single = 3.5
Dim i As Integer = CType(d, Integer) ' set to 4 (Banker's rounding)
i = CInt(d) ' same result as CType
i = Int(d) ' set to 3 (Int function truncates the decimal)

Value Types
bool
byte, sbyte
char
short, ushort, int, uint, long, ulong
float, double
decimal
DateTime (not a built-in C# type)

Reference Types
object
string

Initializing
bool correct = true;
byte b = 0x2A; // hex

object person = null;
string name = "Dwight";
char grade = 'B';
DateTime today = DateTime.Parse("12/31/2007 12:15:00");
decimal amount = 35.99m;
float gpa = 2.9f;
double pi = 3.14159265;
long lTotal = 123456L;
short sTotal = 123;
ushort usTotal = 123;
uint uiTotal = 123;
ulong ulTotal = 123;

Type Information
int x;
Console.WriteLine(x.GetType()); // Prints System.Int32
Console.WriteLine(typeof(int)); // Prints System.Int32
Console.WriteLine(x.GetType().Name); // prints Int32

Type Conversion
float d = 3.5f;
int i = (int)d; // set to 3 (truncates decimal)

Const MAX_STUDENTS As Integer = 25

' Can set to a const or var; may be initialized in a constructor
ReadOnly MIN_DIAMETER As Single = 4.93

const int MAX_STUDENTS = 25;

// Can set to a const or var; may be initialized in a constructor
readonly float MIN_DIAMETER = 4.93f;

Enum Action
Start
[Stop] ' Stop is a reserved word
Rewind
Forward
End Enum

Enum Status
Flunk = 50
Pass = 70
Excel = 90
End Enum

Dim a As Action = Action.Stop
If a <> Action.Start Then _
Console.WriteLine(a.ToString & " is " & a) ' Prints "Stop is 1"

Console.WriteLine(Status.Pass) ' Prints 70
Console.WriteLine(Status.Pass.ToString()) ' Prints Pass

enum Action {Start, Stop, Rewind, Forward};
enum Status {Flunk = 50, Pass = 70, Excel = 90};

Action a = Action.Stop;
if (a != Action.Start)
Console.WriteLine(a + " is " + (int) a); // Prints "Stop is 1"

Console.WriteLine((int) Status.Pass); // Prints 70
Console.WriteLine(Status.Pass); // Prints Pass

Comparison
= < > <= >= <>

Arithmetic
+ - * /
Mod
\ (integer division)
^ (raise to a power)

Assignment
= += -= *= /= \= ^= <<= >>= &=

Bitwise
And Or Xor Not << >>

Logical
AndAlso OrElse And Or Xor Not

Note: AndAlso and OrElse perform short-circuit logical evaluations

String Concatenation
&

Comparison
== < > <= >= !=

Arithmetic
+ - * /
% (mod)
/ (integer division if both operands are ints)
Math.Pow(x, y)

Assignment
= += -= *= /= %= &= |= ^= <<= >>= ++ --

Bitwise
& | ^ ~ << >>

Logical
&& || & | ^ !

Note: && and || perform short-circuit logical evaluations

String Concatenation
+

' Ternary/Conditional operator (Iff evaluates 2nd and 3rd expressions)
greeting = If(age <>

' One line doesn't require "End If"
If age <>Then greeting = "What's up?"
If age <>Then greeting = "What's up?" Else greeting = "Hello"

' Use : to put two commands on same line
If x <> 100 AndAlso y <>Then x *= 5 : y *= 2

' Preferred
If x <> 100 AndAlso y <>Then
x *= 5
y *= 2
End If

' To break up any long single line use _
If whenYouHaveAReally < longLine And _
itNeedsToBeBrokenInto2 > Lines Then _
UseTheUnderscore(charToBreakItUp)

'If x > 5 Then
x *= y
ElseIf x = 5 OrElse y Mod 2 = 0 Then
x += y
ElseIf x <>Then
x -= y
Else
x /= y
End If

Select Case color ' Must be a primitive data type
Case "pink", "red"
r += 1
Case "blue"
b += 1
Case "green"
g += 1
Case Else
other += 1
End Select

// Ternary/Conditional operator
greeting = age <>? "What's up?" : "Hello";

if (age < 20)
greeting = "What's up?";
else
greeting = "Hello";

// Multiple statements must be enclosed in {}
if (x != 100 && y < 5) {
x *= 5;
y *= 2;
}

No need for _ or : since ; is used to terminate each statement.

if (x > 5)
x *= y;
else if (x == 5 || y % 2 == 0)
x += y;
else if (x < 10)
x -= y;
else
x /= y;

// Every case must end with break or goto case
switch (color) { // Must be integer or string
case "pink":
case "red": r++; break;
case "blue": b++; break;
case "green": g++; break;
default: other++; break; // break necessary on default
}

Pre-test Loops:
While c < 10 c += 1 End While	Do Until c = 10 c += 1 Loop
Do While c < 10 c += 1 Loop	For c = 2 To 10 Step 2 Console.WriteLine(c) Next
Post-test Loops:
Do c += 1 Loop While c <>	Do c += 1 Loop Until c = 10

' Array or collection looping
Dim names As String() = {"Fred", "Sue", "Barney"}
For Each s As String In names
Console.WriteLine(s)
Next

' Breaking out of loops
Dim i As Integer = 0
While (True)
If (i = 5) Then Exit While
i += 1
End While

' Continue to next iteration
For i = 0 To 4
If i <>Continue For
Console.WriteLine(i) ' Only prints 4
Next

Pre-test Loops:

// no "until" keyword
while (c < 10)
c++;

for (c = 2; c <= 10; c += 2)
Console.WriteLine(c);

Post-test Loop:

do
c++;
while (c < 10);

// Array or collection looping
string[] names = {"Fred", "Sue", "Barney"};
foreach (string s in names)
Console.WriteLine(s);

// Breaking out of loops
int i = 0;
while (true) {
if (i == 5)
break;
i++;
}

// Continue to next iteration
for (i = 0; i < 5; i++) {
if (i < 4)
continue;
Console.WriteLine(i); // Only prints 4
}

Dim nums() As Integer = {1, 2, 3}
For i As Integer = 0 To nums.Length - 1
Console.WriteLine(nums(i))
Next

' 4 is the index of the last element, so it holds 5 elements
Dim names(4) As String
names(0) = "David"
names(5) = "Bobby" ' Throws System.IndexOutOfRangeException

' Resize the array, keeping the existing values (Preserve is optional)
ReDim Preserve names(6)

Dim twoD(rows-1, cols-1) As Single
twoD(2, 0) = 4.5

Dim jagged()() As Integer = { _
New Integer(4) {}, New Integer(1) {}, New Integer(2) {} }
jagged(0)(4) = 5

int[] nums = {1, 2, 3};
for (int i = 0; i < nums.Length; i++)
Console.WriteLine(nums[i]);

// 5 is the size of the array
string[] names = new string[5];
names[0] = "David";
names[5] = "Bobby"; // Throws System.IndexOutOfRangeException

// C# can't dynamically resize an array. Just copy into new array.
string[] names2 = new string[7];
Array.Copy(names, names2, names.Length); // or names.CopyTo(names2, 0);

float[,] twoD = new float[rows, cols];
twoD[2,0] = 4.5f;

int[][] jagged = new int[3][] {
new int[5], new int[2], new int[3] };
jagged[0][4] = 5;

' Pass by value (in, default), reference (in/out), and reference (out)
Sub TestFunc(ByVal x As Integer, ByRef y As Integer, ByRef z As Integer)
x += 1
y += 1
z = 5
End Sub

Dim a = 1, b = 1, c As Integer ' c set to zero by default
TestFunc(a, b, c)
Console.WriteLine("{0} {1} {2}", a, b, c) ' 1 2 5

' Accept variable number of arguments
Function Sum(ByVal ParamArray nums As Integer()) As Integer
Sum = 0
For Each i As Integer In nums
Sum += i
Next
End Function ' Or use Return statement like C#

Dim total As Integer = Sum(4, 3, 2, 1) ' returns 10

' Optional parameters must be listed last and must have a default value
Sub SayHello(ByVal name As String, Optional ByVal prefix As String = "")
Console.WriteLine("Greetings, " & prefix & " " & name)
End Sub

SayHello("Strangelove", "Dr.")
SayHello("Madonna")

// Pass by value (in, default), reference (in/out), and reference (out)
void TestFunc(int x, ref int y, out int z) {
x++;
y++;
z = 5;
}

int a = 1, b = 1, c; // c doesn't need initializing
TestFunc(a, ref b, out c);
Console.WriteLine("{0} {1} {2}", a, b, c); // 1 2 5

// Accept variable number of arguments
int Sum(params int[] nums) {
int sum = 0;
foreach (int i in nums)
sum += i;
return sum;
}

int total = Sum(4, 3, 2, 1); // returns 10

/* C# doesn't support optional arguments/parameters. Just create two different versions of the same function. */
void SayHello(string name, string prefix) {
Console.WriteLine("Greetings, " + prefix + " " + name);
}

void SayHello(string name) {
SayHello(name, "");
}

Special character constants (all also accessible from ControlChars class)
vbCrLf, vbCr, vbLf, vbNewLine
vbNullString
vbTab
vbBack
vbFormFeed
vbVerticalTab
""

' String concatenation (use & or +)
Dim school As String = "Harding" & vbTab
school = school & "University" ' school is "Harding (tab) University"

' Chars
Dim letter As Char = school.Chars(0) ' letter is H
letter = Convert.ToChar(65) ' letter is A
letter = Chr(65) ' same thing
Dim word() As Char = school.ToCharArray() ' word holds Harding

' No string literal operator
Dim msg As String = "File is c:\temp\x.dat"

' String comparison
Dim mascot As String = "Bisons"
If (mascot = "Bisons") Then ' true
If (mascot.Equals("Bisons")) Then ' true
If (mascot.ToUpper().Equals("BISONS")) Then ' true
If (mascot.CompareTo("Bisons") = 0) Then ' true

' String matching with Like - Regex is more powerful
If ("John 3:16" Like "Jo[Hh]? #:*") Then 'true

' Substring
s = mascot.Substring(2, 3)) ' s is "son"

' Replacement
s = mascot.Replace("sons", "nomial")) ' s is "Binomial"

' Split
Dim names As String = "Frank,Becky,Ethan,Braden"
Dim parts() As String = names.Split(",".ToCharArray()) ' One name in each slot

' Date to string
Dim dt As New DateTime(1973, 10, 12)
Dim s As String = "My birthday: " & dt.ToString("MMM dd, yyyy") ' Oct 12, 1973

' Integer to String
Dim x As Integer = 2
Dim y As String = x.ToString() ' y is "2"

' String to Integer
Dim x As Integer = Convert.ToInt32("-5") ' x is -5

' Mutable string
Dim buffer As New System.Text.StringBuilder("two ")
buffer.Append("three ")
buffer.Insert(0, "one ")
buffer.Replace("two", "TWO")
Console.WriteLine(buffer) ' Prints "one TWO three"

Escape sequences
\r // carriage-return
\n // line-feed
\t // tab
\\ // backslash
\" // quote

// String concatenation
string school = "Harding\t";
school = school + "University"; // school is "Harding (tab) University"

// Chars
char letter = school[0]; // letter is H
letter = Convert.ToChar(65); // letter is A
letter = (char)65; // same thing
char[] word = school.ToCharArray(); // word holds Harding

// String literal
string msg = @"File is c:\temp\x.dat";
// same as
string msg = "File is c:\\temp\\x.dat";

// String comparison
string mascot = "Bisons";
if (mascot == "Bisons") // true
if (mascot.Equals("Bisons")) // true
if (mascot.ToUpper().Equals("BISONS")) // true
if (mascot.CompareTo("Bisons") == 0) // true

// String matching - No Like equivalent, use Regex

// Substring
s = mascot.Substring(2, 3)) // s is "son"

// Replacement
s = mascot.Replace("sons", "nomial")) // s is "Binomial"

// Split
string names = "Frank,Becky,Ethan,Braden";
string[] parts = names.Split(",".ToCharArray()); // One name in each slot

// Date to string
DateTime dt = new DateTime(1973, 10, 12);
string s = dt.ToString("MMM dd, yyyy"); // Oct 12, 1973

// int to string
int x = 2;
string y = x.ToString(); // y is "2"

// string to int
int x = Convert.ToInt32("-5"); // x is -5

// Mutable string
System.Text.StringBuilder buffer = new System.Text.StringBuilder("two ");
buffer.Append("three ");
buffer.Insert(0, "one ");
buffer.Replace("two", "TWO");
Console.WriteLine(buffer); // Prints "one TWO three"

Imports System.Text.RegularExpressions

' Match a string pattern
Dim r As New Regex("j[aeiou]h?. \d:*", RegexOptions.IgnoreCase Or _
RegexOptions.Compiled)
If (r.Match("John 3:16").Success) Then 'true
Console.WriteLine("Match")
End If

' Find and remember all matching patterns
Dim s As String = "My number is 305-1881, not 305-1818."
Dim r As New Regex("(\d+-\d+)")
Dim m As Match = r.Match(s) ' Matches 305-1881 and 305-1818
While m.Success
Console.WriteLine("Found number: " & m.Groups(1).Value & " at position " _
& m.Groups(1).Index.ToString)
m = m.NextMatch()
End While

' Remeber multiple parts of matched pattern
Dim r As New Regex("(\d\d):(\d\d) (am|pm)")
Dim m As Match = r.Match("We left at 03:15 pm.")
If m.Success Then
Console.WriteLine("Hour: " & m.Groups(1).ToString) ' 03
Console.WriteLine("Min: " & m.Groups(2).ToString) ' 15
Console.WriteLine("Ending: " & m.Groups(3).ToString) ' pm
End If

' Replace all occurrances of a pattern
Dim r As New Regex("h\w+?d", RegexOptions.IgnoreCase)
Dim s As String = r.Replace("I heard this was HARD!", "easy") ' I easy this was easy!

' Replace matched patterns
Dim s As String = Regex.Replace("123 <> $1") ' 456 > 123

' Split a string based on a pattern
Dim names As String = "Frank, Becky, Ethan, Braden"
Dim r As New Regex(",\s*")
Dim parts() As String = r.Split(names) ' One name in each slot

using System.Text.RegularExpressions;

// Match a string pattern
Regex r = new Regex(@"j[aeiou]h?. \d:*", RegexOptions.IgnoreCase |
RegexOptions.Compiled);
if (r.Match("John 3:16").Success) // true
Console.WriteLine("Match");

// Find and remember all matching patterns
string s = "My number is 305-1881, not 305-1818.";
Regex r = new Regex("(\\d+-\\d+)");
// Matches 305-1881 and 305-1818
for (Match m = r.Match(s); m.Success; m = m.NextMatch())
Console.WriteLine("Found number: " + m.Groups[1] + " at position " +
m.Groups[1].Index);

// Remeber multiple parts of matched pattern
Regex r = new Regex("@(\d\d):(\d\d) (am|pm)");
Match m = r.Match("We left at 03:15 pm.");
if (m.Success) {
Console.WriteLine("Hour: " + m.Groups[1]); // 03
Console.WriteLine("Min: " + m.Groups[2]); // 15
Console.WriteLine("Ending: " + m.Groups[3]); // pm
}

// Replace all occurrances of a pattern
Regex r = new Regex("h\\w+?d", RegexOptions.IgnoreCase);
string s = r.Replace("I heard this was HARD!", "easy")); // I easy this was easy!

// Replace matched patterns
string s = Regex.Replace("123 <> $1"); // 456 > 123

// Split a string based on a pattern
string names = "Frank, Becky, Ethan, Braden";
Regex r = new Regex(@",\s*");
string[] parts = r.Split(names); // One name in each slot

' Throw an exception
Dim ex As New Exception("Something is really wrong.")
Throw ex

' Catch an exception
Try
y = 0
x = 10 / y
Catch ex As Exception When y = 0 ' Argument and When is optional
Console.WriteLine(ex.Message)
Finally
Beep()
End Try

' Deprecated unstructured error handling
On Error GoTo MyErrorHandler
...
MyErrorHandler: Console.WriteLine(Err.Description)

// Throw an exception
Exception up = new Exception("Something is really wrong.");
throw up; // ha ha

// Catch an exception
try {
y = 0;
x = 10 / y;
}
catch (Exception ex) { // Argument is optional, no "When" keyword
Console.WriteLine(ex.Message);
}
finally {
Microsoft.VisualBasic.Interaction.Beep();
}

Namespace Harding.Compsci.Graphics
...
End Namespace

' or

Namespace Harding
Namespace Compsci
Namespace Graphics
...
End Namespace
End Namespace
End Namespace

Imports Harding.Compsci.Graphics

namespace Harding.Compsci.Graphics {
...
}

// or

namespace Harding {
namespace Compsci {
namespace Graphics {
...
}
}
}

using Harding.Compsci.Graphics;

Accessibility keywords
Public
Private
Friend
Protected
Protected Friend
Shared

' Inheritance
Class FootballGame
Inherits Competition
...
End Class

' Interface definition
Interface IAlarmClock
...
End Interface

// Extending an interface
Interface IAlarmClock
Inherits IClock
...
End Interface

// Interface implementation
Class WristWatch
Implements IAlarmClock, ITimer
...
End Class

Accessibility keywords
public
private
internal
protected
protected internal
static

// Inheritance
class FootballGame : Competition {
...
}

// Interface definition
interface IAlarmClock {
...
}

// Extending an interface
interface IAlarmClock : IClock {
...
}

// Interface implementation
class WristWatch : IAlarmClock, ITimer {
...
}

Class SuperHero
Private _powerLevel As Integer

Public Sub New()
_powerLevel = 0
End Sub

Public Sub New(ByVal powerLevel As Integer)
Me._powerLevel = powerLevel
End Sub

Protected Overrides Sub Finalize()
' Desctructor code to free unmanaged resources
MyBase.Finalize()
End Sub
End Class

class SuperHero {
private int _powerLevel;

public SuperHero() {
_powerLevel = 0;
}

public SuperHero(int powerLevel) {
this._powerLevel= powerLevel;
}

~SuperHero() {
// Destructor code to free unmanaged resources.
// Implicitly creates a Finalize method
}
}

Dim hero As SuperHero = New SuperHero
' or
Dim hero As New SuperHero

With hero
.Name = "SpamMan"
.PowerLevel = 3
End With

hero.Defend("Laura Jones")
hero.Rest() ' Calling Shared method
' or
SuperHero.Rest()

Dim hero2 As SuperHero = hero ' Both reference the same object
hero2.Name = "WormWoman"
Console.WriteLine(hero.Name) ' Prints WormWoman

hero = Nothing ' Free the object

If hero Is Nothing Then _
hero = New SuperHero

Dim obj As Object = New SuperHero
If TypeOf obj Is SuperHero Then _
Console.WriteLine("Is a SuperHero object.")

' Mark object for quick disposal
Using reader As StreamReader = File.OpenText("test.txt")
Dim line As String = reader.ReadLine()
While Not line Is Nothing
Console.WriteLine(line)
line = reader.ReadLine()
End While
End Using

SuperHero hero = new SuperHero();

// No "With" construct
hero.Name = "SpamMan";
hero.PowerLevel = 3;

hero.Defend("Laura Jones");
SuperHero.Rest(); // Calling static method

SuperHero hero2 = hero; // Both reference the same object
hero2.Name = "WormWoman";
Console.WriteLine(hero.Name); // Prints WormWoman

hero = null ; // Free the object

if (hero == null)
hero = new SuperHero();

Object obj = new SuperHero();
if (obj is SuperHero)
Console.WriteLine("Is a SuperHero object.");

// Mark object for quick disposal
using (StreamReader reader = File.OpenText("test.txt")) {
string line;
while ((line = reader.ReadLine()) != null)
Console.WriteLine(line);
}

Structure StudentRecord
Public name As String
Public gpa As Single

Public Sub New(ByVal name As String, ByVal gpa As Single)
Me.name = name
Me.gpa = gpa
End Sub
End Structure

Dim stu As StudentRecord = New StudentRecord("Bob", 3.5)
Dim stu2 As StudentRecord = stu

stu2.name = "Sue"
Console.WriteLine(stu.name) ' Prints Bob
Console.WriteLine(stu2.name) ' Prints Sue

struct StudentRecord {
public string name;
public float gpa;

public StudentRecord(string name, float gpa) {
this.name = name;
this.gpa = gpa;
}
}

StudentRecord stu = new StudentRecord("Bob", 3.5f);
StudentRecord stu2 = stu;

stu2.name = "Sue";
Console.WriteLine(stu.name); // Prints Bob
Console.WriteLine(stu2.name); // Prints Sue

Private _size As Integer

Public Property Size() As Integer
Get
Return _size
End Get
Set (ByVal Value As Integer)
If Value < 0 Then
_size = 0
Else
_size = Value
End If
End Set
End Property

foo.Size += 1

private int _size;

public int Size {
get {
return _size;
}
set {
if (value < 0)
_size = 0;
else
_size = value;
}
}

foo.Size++;

Delegate Sub MsgArrivedEventHandler(ByVal message As String)

Event MsgArrivedEvent As MsgArrivedEventHandler

' or to define an event which declares a delegate implicitly
Event MsgArrivedEvent(ByVal message As String)

AddHandler MsgArrivedEvent, AddressOf My_MsgArrivedCallback
' Won't throw an exception if obj is Nothing
RaiseEvent MsgArrivedEvent("Test message")
RemoveHandler MsgArrivedEvent, AddressOf My_MsgArrivedCallback

Imports System.Windows.Forms

Dim WithEvents MyButton As Button ' WithEvents can't be used on local variable
MyButton = New Button

Private Sub MyButton_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyButton.Click
MessageBox.Show(Me, "Button was clicked", "Info", _
MessageBoxButtons.OK, MessageBoxIcon.Information)
End Sub

delegate void MsgArrivedEventHandler(string message);

event MsgArrivedEventHandler MsgArrivedEvent;

// Delegates must be used with events in C#

MsgArrivedEvent += new MsgArrivedEventHandler(My_MsgArrivedEventCallback);
MsgArrivedEvent("Test message"); // Throws exception if obj is null
MsgArrivedEvent -= new MsgArrivedEventHandler(My_MsgArrivedEventCallback);

using System.Windows.Forms;

Button MyButton = new Button();
MyButton.Click += new System.EventHandler(MyButton_Click);

private void MyButton_Click(object sender, System.EventArgs e) {
MessageBox.Show(this, "Button was clicked", "Info",
MessageBoxButtons.OK, MessageBoxIcon.Information);
}

Console.Write("What's your name? ")
Dim name As String = Console.ReadLine()
Console.Write("How old are you? ")
Dim age As Integer = Val(Console.ReadLine())
Console.WriteLine("{0} is {1} years old.", name, age)
' or
Console.WriteLine(name & " is " & age & " years old.")

Dim c As Integer
c = Console.Read() ' Read single char
Console.WriteLine(c) ' Prints 65 if user enters "A"

Console.Write("What's your name? ");
string name = Console.ReadLine();
Console.Write("How old are you? ");
int age = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("{0} is {1} years old.", name, age);
// or
Console.WriteLine(name + " is " + age + " years old.");

int c = Console.Read(); // Read single char
Console.WriteLine(c); // Prints 65 if user enters "A"

Imports System.IO

' Write out to text file
Dim writer As StreamWriter = File.CreateText("c:\myfile.txt")
writer.WriteLine("Out to file.")
writer.Close()

' Read all lines from text file
Dim reader As StreamReader = File.OpenText("c:\myfile.txt")
Dim line As String = reader.ReadLine()
While Not line Is Nothing
Console.WriteLine(line)
line = reader.ReadLine()
End While
reader.Close()

' Write out to binary file
Dim str As String = "Text data"
Dim num As Integer = 123
Dim binWriter As New BinaryWriter(File.OpenWrite("c:\myfile.dat"))
binWriter.Write(str)
binWriter.Write(num)
binWriter.Close()

' Read from binary file
Dim binReader As New BinaryReader(File.OpenRead("c:\myfile.dat"))
str = binReader.ReadString()
num = binReader.ReadInt32()
binReader.Close()

using System.IO;

// Write out to text file
StreamWriter writer = File.CreateText("c:\\myfile.txt");
writer.WriteLine("Out to file.");
writer.Close();

// Read all lines from text file
StreamReader reader = File.OpenText("c:\\myfile.txt");
string line = reader.ReadLine();
while (line != null) {
Console.WriteLine(line);
line = reader.ReadLine();
}
reader.Close();

// Write out to binary file
string str = "Text data";
int num = 123;
BinaryWriter binWriter = new BinaryWriter(File.OpenWrite("c:\\myfile.dat"));
binWriter.Write(str);
binWriter.Write(num);
binWriter.Close();

// Read from binary file
BinaryReader binReader = new BinaryReader(File.OpenRead("c:\\myfile.dat"));
str = binReader.ReadString();
num = binReader.ReadInt32();
binReader.Close();

Equivalent keyword C# 's typeof() in VB

2009-12-08T05:18:00.000-08:00

Equivalent keyword in typeof()1

...is in C#...

typeof(Foo)

...is in VB...it's...

GetType(Foo)

Usage of @MasterType

2009-11-26T01:52:00.000-08:00

The @MasterType Page Declarative of a page is used to access the public properties and methods of a master page to the sub level of content page

Example :

Step 1:
<%@ Master Language="C#" AutoEventWireup="true" CodeFile="MasterPage.master.cs" Inherits="MasterPage_MasterPage" %>

<title>ScriptManager in Master Page Example</title>

<form id="form1" runat="server">
<div>
<asp:scriptmanager id="ScriptManager1" runat="server">
<asp:panel id="MasterPanel1" runat="server" groupingtext="Master Page">
<asp:button id="Button1" runat="server" text="Full Page Refresh">
<asp:button id="Button2" runat="server" text="Refresh Panel" onclick="MasterButton2_Click">
</asp:button>
<asp:contentplaceholder id="ContentPlaceHolder1" runat="server">
</asp:contentplaceholder>
</asp:button></asp:panel></asp:scriptmanager></div>
</form>

Step 2:

Create a public property in the MasterPage.master.cs

public partial class MasterPage_MasterPage : System.Web.UI.MasterPage
{
public DateTime LastUpdate
{
get
{
return (DateTime)(ViewState["LastUpdate"] ?? DateTime.Now);
}
set
{
ViewState["LastUpdate"] = value;
}
}
}

Step 3:

Define the <%@ MasterType %> like this

<%@ Page Language="C#" MasterPageFile="~/MasterPage/MasterPage.master" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="MasterPage_Default" Title="Untitled Page" %>



<%@ MasterType VirtualPath="~/MasterPage/MasterPage.master" %>

<asp:content id="Content1" contentplaceholderid="ContentPlaceHolder1" runat="Server">
<asp:panel id="Panel2" groupingtext="ContentPage" runat="server">
<asp:updatepanel id="UpdatePanel1" updatemode="Conditional" runat="server">
<contenttemplate>
<p>
Last updated: <strong><%= Master.LastUpdate.ToString() %></strong>
</p>
<asp:button id="Button3" text="Refresh Panel" onclick="Button3_Click" runat="server">
</asp:button>
</contenttemplate>
</asp:updatepanel>
</asp:panel>

Step 4:

Then we can use to access the public methods and properties from master page to content page.

protected void Button3_Click(object sender, EventArgs e)
{
Master.LastUpdate = DateTime.Now;
}

PageRequestManager

2009-11-24T06:28:00.000-08:00

var prm = Sys.WebForms.PageRequestManager.getInstance();

prm.add_pageLoaded(PageLoadedEventHandler);

function PageLoadedEventHandler()

{

alert("Inside PageLoadedEventHandler Working");

}

Sys.WebForms.PageRequestManager.getInstance().add_initializeRequest(InitializeRequest);

function InitializeRequest()

{

alert('Initial requets inside...');

}

By this way, we can fire all the Five ajax page life cycle events.

Ajax + asp.net Page life cycle

2009-11-24T06:06:00.000-08:00

Client Page Life-cycle Events

During ordinary page processing in the browser, the window.onload DOM event is raised when the page first loads. Similarly, the window.onunload DOM event is raised when the page is refreshed or when the user moves away from the page.

However, these events are not raised during asynchronous postbacks. To help you manage these types of events for asynchronous postbacks, the PageRequestManager class exposes a set of events. These resemble window.load and other DOM events, but they also occur during asynchronous postbacks. For each asynchronous postback, all page events in the PageRequestManager class are raised and any attached event handlers are called.

Note:
For synchronous postbacks, only the pageLoaded event is raised.

You can write client script to handle events raised by the PageRequestManager class. Different event argument objects are passed to handlers for different events. The following table summarizes the PageRequestManager class events and the corresponding event argument classes. The order of the events in the table is the order of the events for a single asynchronous postback without errors.

initializeRequest: Raised before the request is initialized for an asynchronous postback. Event data is passed to handlers as an InitializeRequestEventArgs object. The object makes available the element that caused the postback and the underlying request object.
beginRequest: Raised just before the asynchronous postback is sent to the server. Event data is passed to handlers as a BeginRequestEventArgs object. The object makes available the element that caused the postback and the underlying request object.
pageLoading: Raised after the response to the most recent asynchronous postback has been received but before any updates to the page have been made. Event data is passed to handlers as a PageLoadingEventArgs object. The object makes available information about what panels will be deleted and updated as a result of the most recent asynchronous postback.
pageLoaded: Raised after page regions are updated after the most recent postback. Event data is passed to handlers as a PageLoadedEventArgs object. The object makes available information about what panels were created or updated. For synchronous postbacks, panels can only be created, but for asynchronous postbacks, panels can be both created and updated.
endRequest: Raised when request processing is finished. Event data is passed to handlers as an EndRequestEventArgs object. The object makes available information about errors that have occurred and whether the error was handled. It also makes available the response object.

For creating and adding Dynamic templated column using Itemplate interface

2009-11-23T22:40:00.000-08:00

First have to override the OnIt() method and then we can add the TemplatedColumn in it for creating check box control.

protected override void OnInit(EventArgs e)

{

base.OnInit(e);

// Create a templated column

TemplatedColumn col = new TemplatedColumn(true);

this.UltraWebGrid1.DisplayLayout.Bands[0].Columns.Add(col);

col.Key = "CheckBoxCol";

col.Header.Caption = "";

GridHeaderTemplate tempHeader = new GridHeaderTemplate();

// Set the header template.

col.HeaderTemplate = tempHeader;

this.UltraWebGrid1.DataSource = LoadGrid();

this.UltraWebGrid1.DataBind();

}

/// Class with implementing the ITemplate

-----------------------------------------------------------

public class GridHeaderTemplate : ITemplate

{

public void InstantiateIn(Control container)

{

// Cast the container to a HeaderItem

HeaderItem headerItem = (HeaderItem)container;

CheckBox checkBox = new CheckBox();

CheckBox cb = new CheckBox();

cb.ID = "headerCB";

cb.Attributes.Add("onclick", "HeaderCheckedChanged();");

headerItem.Controls.Add(cb);

}

.net Features in C# 3.5

2009-11-20T04:35:00.000-08:00

. Automatic Property setters/getters

Whenever you declare a class, most of the times the class is used only as a placeholder with getters and setters for holding property values without any additional logic. For example, consider a simple class like the following:

public class Person
{
int _id;
string _firstName;
string _lastName;
public int ID { get{return _id;} set{_id = value;} }
public string FirstName { get{return _firstName;} set{_firstName = value;} }
public string LastName { get{return _lastName;} set{_lastName = value;} }
public string FullName { get{return FirstName + " " + LastName;} }
}

As you can see from the above class declaration, it doesn't contain any additional logic. The get and set properties are repetitive and they simply set or get the values of the properties without adding any value. In C#, you can simplify that by leveraging the new feature named Auto-Implemented properties. By taking advantage of this new feature, you can rewrite the above code as follows:

public class Person
{
public int ID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string FullName
{
get
{
return FirstName + " " + LastName;
}
private set {;}
}
}

In the above code, when you declare a property, the compiler automatically creates a private, anonymous field that is available only to the property's get and set accessors. Note that the auto implemented properties must declare both a get and set accessor. However if you need to create a read-only property, modify the scope of the set accessor to be private.

· Object Initializers
· Collection Initializers
· Extension Methods
· Implicitly Typed Variable
· Anonymous Types

New features in asp.net 3.5
////-----------------------------

. ASP.NET AJAX
. New Controls (ListView and DataPager)
. New Data Source Control (LinqDataSource)
. LINQ (Language Integrated Query)
. ASP.NET Merge Tool:
(ASP.NET 3.5 includes a new merge tool (aspnet_merge.exe). This tool lets you combine and manage assemblies created by aspnet_compiler.exe)
. New Assemblies
· System.Core.dll - Includes the implementation for LINQ to Objects
· System.Data.Linq.dll - Includes the implementation for LINQ to SQL
· System.Xml.Linq.dll - Includes the implementation for LINQ to XML
· System.Data.DataSetExtensions.dll - Includes the implementation for LINQ to DataSet

.Net Framework 3.0 features

2009-11-20T04:31:00.000-08:00

Framework 3.0 features:

. Implicitly typed local variables

// i is compiled as an int
var i = 5;

// s is compiled as a string
var s = "Hello";

// a is compiled as int[]
var a = new[] { 0, 1, 2 };

// expr is compiled as IEnumerable
// or perhaps IQueryable
var expr =
from c in customers
where c.City == "London"
select c;

// anon is compiled as an anonymous type
var anon = new { Name = "Terry", Age = 34 };

// list is compiled as List
var list = new List();

. Anonymous types

C# 3.0 gives you the flexibility to create an instance of a class without having to write code for the class beforehand. So, you now can write code as shown below:

new {hair="black", skin="green", teethCount=64}
The preceding line of code, with the help of the "new" keyword, gives you a new type that has three properties: hair, skin, and teethCount. Behind the scenes, the C# compiler would create a class that looks as follows:

class __Anonymous1
{
private string _hair = "black";
private string _skin = "green";
private int _teeth = 64;
public string hair {get { return _hair; } set { _hair = value; }}
public string skin {get { return _skin; } set { _skin = value; }}
public int teeth {get { return _teeth; } set { _teeth = value; }}
}

. Extension methods

Extension methods enable you to extend various types with additional static methods. However, they are quite limited and should be used as a last resort—only where instance methods are insufficient.

Extension methods can be declared only in static classes and are identified by the keyword "this" as a modifier on the first parameter of the method. The following is an example of a valid extension method:

public static int ToInt32(this string s)
{
return Convert.ToInt32(s) ;
}

If the static class that contains the above method is imported using the "using" keyword, the ToInt32 method will appear in existing types (albeit in lower precedence to existing instance methods), and you will be able to compile and execute code that looks as follows:

string s = "1";
int i = s.ToInt32();

This allows you to take advantage of the extensible nature of various built-in or defined types and add newer methods to them.

. Object and collection initializers

public class CoOrdinate
{
public int x ;
public int y;
}

You then could declare and initialize a CoOrdinate object using an object initializer, like this:

var myCoOrd = new CoOrdinate{ x = 0, y= 0} ;
The above code may have made you raise your eyebrows and ask, "Why not just write the following:"

var myCoOrd = new CoOrdinate(0, 0) ;

Note: I never declared a constructor that accepted two parameters in my class. In fact, initializing the object using an object initializer essentially is equivalent to calling a parameterless (default) constructor of the CoOrdinate object and then assigning the relevant values.Similarly, you should easily be able to give values to Collections in a rather concise and compact manner in C# 3.0.For instance, the following C# 2.0 code:

List animals = new List();
animals.Add("monkey");
animals.Add("donkey");
animals.Add("cow");
animals.Add("dog");
animals.Add("cat");

Now can be shortened to simply:

List animals = new List {
"monkey", "donkey", "cow", "dog", "cat" } ;

. Lambda expressions

It Allowes you to write code blocks in methods, which you could invoke easily using delegates. Delegates are definitely useful, and they are used throughout the framework, but in many instances you had to declare a method or a class just to use one. Thus, to give you an easier and more concise way of writing code, C# 2.0 allowed you to replace standard calls to delegates with anonymous methods. The following code may have been written in .NET 1.1 or earlier:

class Program
{
delegate void DemoDelegate();
static void Main(string[] args)
{
DemoDelegate myDelegate = new DemoDelegate(SayHi);
myDelegate();
}
void SayHi()
{
Console.Writeline("Hiya!!") ;
}
}

In C# 2.0, using anonymous methods, you could rewrite the code as follows:

class Program
{
delegate void DemoDelegate();
static void Main(string[] args)
{
DemoDelegate myDelegate = delegate()
{
Console.Writeline("Hiya!!");
};
myDelegate();
}
}

Lambda expressions are simply functions and they are declared in the context of expressions than as a member of a class. It is an inline expression or a statement block which can be used to pass arguments to a method or assign value to delegate. All lambda expressions use the lambda operator => and the left side of the operator denotes the results and the right side contains the expression to be evaluated. For instance, consider the following lambda expression:

age => age + 1;

The above function takes one argument named age, and returns age + 1 as the result. As you can see, Lambda expressions follow the below syntax:

(parameter-list) => expression;

where expression can be any C# expression or a block of code. Just like anonymous methods you can use a lambda expression in place of a delegate. Here are some sample lambda expressions and their corresponding delegates.

//Explicitly typed parameter
(Person obj) => MessageBox.Show(obj.FirstName.ToUpper());

//Implicitly typed parameter
(obj) => obj.FirstName == "Thiru";

//Explicitly typed parameter
(int a, int b) => a + b

//Implicitly typed parameter
(x, y) => { return x + y; }

As you see from the preceding lines of code, lambda expressions can be written in such a way that itcan infer the parameter type from the signature of the delegate it is assigned to.

. Query expressions

Even though further enhancements may be introduced in the coming months as C# 3.0 matures, the new features described in the preceding sections make it a lot easier to work with data inside C# in general. This feature, also known as LINQ (Language Integrated Query), allows you to write SQL-like syntax in C#.

For instance, you may have a class that describes your data as follows:

public class CoOrdinate
{
public int x ;
public int y;
}

You now could easily declare the logical equivalent of a database table inside C# as follows:

// Use Object and collection initializers
List coords = ... ;

And now that you have your data as a collection that implements IEnumerable, you easily can query this data as follows:

var filteredCoords =
from c in coords
where x == 1
select (c.x, c.y)

In the SQL-like syntax above, "from", "where", and "select" are query expressions that take advantage of C# 3.0 features such as anonymous types, extension methods, implicit typed local variables, and so forth. This way, you can leverage SQL-like syntax and work with disconnected data easily.

Each query expression is actually translated into a C#-like invocation behind the scenes. For instance, the following:

where x == 1
Translates to this:

coords.where(c => c.x == 1)
As you can see, the above looks an awful lot like a lambda expression and extension method. C# 3.0 has many other query expressions and rules that surround them.

. Expression Trees

Expression trees represent language-level code in the form of data. The data is stored in a tree-shaped structure. Each node in the expression tree represents an expression, for example a method call or a binary operation such as
x <>> exprTree = num => num < param =" (ParameterExpression)exprTree.Parameters[0];" operation =" (BinaryExpression)exprTree.Body;" left =" (ParameterExpression)operation.Left;" right =" (ConstantExpression)operation.Right;"> {1} {2} {3}",
param.Name, left.Name, operation.NodeType, right.Value);

/* This code produces the following output:

Decomposed expression: num => num LessThan 5
*/

. Implicitly typed arrays.
class ImplicitlyTypedArraySample
{
static void Main()
{
var a = new[] { 1, 10, 100, 1000 }; // int[]
var b = new[] { "hello", null, "world" }; // string[]

// single-dimension jagged array
var c = new[]
{
new[]{1,2,3,4},
new[]{5,6,7,8}
};

// jagged array of strings
var d = new[]
{
new[]{"Luca", "Mads", "Luke", "Dinesh"},
new[]{"Karen", "Suma", "Frances"}
};
}
}

Framework 3.0 Language features:

. WPF
. WCF
. WF

.Net Framework 3.0 features

2009-11-20T04:28:00.000-08:00

.Implicitly typed local variables

// i is compiled as an int
var i = 5;

// s is compiled as a string
var s = "Hello";

// a is compiled as int[]
var a = new[] { 0, 1, 2 };

// expr is compiled as IEnumerable
// or perhaps IQueryable
var expr =
from c in customers
where c.City == "London"
select c;

// anon is compiled as an anonymous type
var anon = new { Name = "Terry", Age = 34 };

// list is compiled as List
var list = new List();

. Anonymous types

C# 3.0 gives you the flexibility to create an instance of a class without having to write code for the class beforehand. So, you now can write code as shown below:

new {hair="black", skin="green", teethCount=64}
The preceding line of code, with the help of the "new" keyword, gives you a new type that has three properties: hair, skin, and teethCount. Behind the scenes, the C# compiler would create a class that looks as follows:

class __Anonymous1
{
private string _hair = "black";
private string _skin = "green";
private int _teeth = 64;
public string hair {get { return _hair; } set { _hair = value; }}
public string skin {get { return _skin; } set { _skin = value; }}
public int teeth {get { return _teeth; } set { _teeth = value; }}
}

. Extension methods

Extension methods enable you to extend various types with additional static methods. However, they are quite limited and should be used as a last resort—only where instance methods are insufficient.

Extension methods can be declared only in static classes and are identified by the keyword "this" as a modifier on the first parameter of the method. The following is an example of a valid extension method:

public static int ToInt32(this string s)
{
return Convert.ToInt32(s) ;
}

If the static class that contains the above method is imported using the "using" keyword, the ToInt32 method will appear in existing types (albeit in lower precedence to existing instance methods), and you will be able to compile and execute code that looks as follows:

string s = "1";
int i = s.ToInt32();

This allows you to take advantage of the extensible nature of various built-in or defined types and add newer methods to them.

. Object and collection initializers

public class CoOrdinate
{
public int x ;
public int y;
}

You then could declare and initialize a CoOrdinate object using an object initializer, like this:

var myCoOrd = new CoOrdinate{ x = 0, y= 0} ;
The above code may have made you raise your eyebrows and ask, "Why not just write the following:"

var myCoOrd = new CoOrdinate(0, 0) ;

Note: I never declared a constructor that accepted two parameters in my class. In fact, initializing the object using an object initializer essentially is equivalent to calling a parameterless (default) constructor of the CoOrdinate object and then assigning the relevant values.Similarly, you should easily be able to give values to Collections in a rather concise and compact manner in C# 3.0.For instance, the following C# 2.0 code:

List animals = new List();
animals.Add("monkey");
animals.Add("donkey");
animals.Add("cow");
animals.Add("dog");
animals.Add("cat");

Now can be shortened to simply:

List animals = new List {
"monkey", "donkey", "cow", "dog", "cat" } ;

. Lambda expressions

It Allowes you to write code blocks in methods, which you could invoke easily using delegates. Delegates are definitely useful, and they are used throughout the framework, but in many instances you had to declare a method or a class just to use one. Thus, to give you an easier and more concise way of writing code, C# 2.0 allowed you to replace standard calls to delegates with anonymous methods. The following code may have been written in .NET 1.1 or earlier:

class Program
{
delegate void DemoDelegate();
static void Main(string[] args)
{
DemoDelegate myDelegate = new DemoDelegate(SayHi);
myDelegate();
}
void SayHi()
{
Console.Writeline("Hiya!!") ;
}
}

In C# 2.0, using anonymous methods, you could rewrite the code as follows:

class Program
{
delegate void DemoDelegate();
static void Main(string[] args)
{
DemoDelegate myDelegate = delegate()
{
Console.Writeline("Hiya!!");
};
myDelegate();
}
}

Lambda expressions are simply functions and they are declared in the context of expressions than as a member of a class. It is an inline expression or a statement block which can be used to pass arguments to a method or assign value to delegate. All lambda expressions use the lambda operator => and the left side of the operator denotes the results and the right side contains the expression to be evaluated. For instance, consider the following lambda expression:

age => age + 1;

The above function takes one argument named age, and returns age + 1 as the result. As you can see, Lambda expressions follow the below syntax:

(parameter-list) => expression;

where expression can be any C# expression or a block of code. Just like anonymous methods you can use a lambda expression in place of a delegate. Here are some sample lambda expressions and their corresponding delegates.

//Explicitly typed parameter
(Person obj) => MessageBox.Show(obj.FirstName.ToUpper());

//Implicitly typed parameter
(obj) => obj.FirstName == "Thiru";

//Explicitly typed parameter
(int a, int b) => a + b

//Implicitly typed parameter
(x, y) => { return x + y; }

As you see from the preceding lines of code, lambda expressions can be written in such a way that itcan infer the parameter type from the signature of the delegate it is assigned to.

. Query expressions

Even though further enhancements may be introduced in the coming months as C# 3.0 matures, the new features described in the preceding sections make it a lot easier to work with data inside C# in general. This feature, also known as LINQ (Language Integrated Query), allows you to write SQL-like syntax in C#.

For instance, you may have a class that describes your data as follows:

public class CoOrdinate
{
public int x ;
public int y;
}

You now could easily declare the logical equivalent of a database table inside C# as follows:

// Use Object and collection initializers
List coords = ... ;

And now that you have your data as a collection that implements IEnumerable, you easily can query this data as follows:

var filteredCoords =
from c in coords
where x == 1
select (c.x, c.y)

In the SQL-like syntax above, "from", "where", and "select" are query expressions that take advantage of C# 3.0 features such as anonymous types, extension methods, implicit typed local variables, and so forth. This way, you can leverage SQL-like syntax and work with disconnected data easily.

Each query expression is actually translated into a C#-like invocation behind the scenes. For instance, the following:

where x == 1
Translates to this:

coords.where(c => c.x == 1)
As you can see, the above looks an awful lot like a lambda expression and extension method. C# 3.0 has many other query expressions and rules that surround them.

. Expression Trees

Expression trees represent language-level code in the form of data. The data is stored in a tree-shaped structure. Each node in the expression tree represents an expression, for example a method call or a binary operation such as
x <>> exprTree = num => num < param =" (ParameterExpression)exprTree.Parameters[0];" operation =" (BinaryExpression)exprTree.Body;" left =" (ParameterExpression)operation.Left;" right =" (ConstantExpression)operation.Right;"> {1} {2} {3}",
param.Name, left.Name, operation.NodeType, right.Value);

/* This code produces the following output:

Decomposed expression: num => num LessThan 5
*/

. Implicitly typed arrays.

class ImplicitlyTypedArraySample
{
static void Main()
{
var a = new[] { 1, 10, 100, 1000 }; // int[]
var b = new[] { "hello", null, "world" }; // string[]

// single-dimension jagged array
var c = new[]
{
new[]{1,2,3,4},
new[]{5,6,7,8}
};

// jagged array of strings
var d = new[]
{
new[]{"Luca", "Mads", "Luke", "Dinesh"},
new[]{"Karen", "Suma", "Frances"}
};
}
}