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Wednesday, August 31, 2011

Delegate-Lambda Expression (=>):

 

 

Lambda Expression  (=>):

 

A lambda expression is an unnamed method written in place of a delegate instance.

The compiler immediately converts the lambda expression to either

 

  • Delegate Instance
  • Unmanaged Method
  • Lambda Expression it introduced in C# 3.0

 

Below is delegate method declaration

 

     public delegate int AddTwoNumberDel(int fvalue, int svalue);

 

     We can use lambda expression

       

                 AddTwoNumberDel AT = (a, b) => a + b;

          int result=   AT(1,2);

          MessageBox.Show(result.ToString());

 

Before that what we used Please check this url

 

http://jsdotnetsupport.blogspot.com/2011/08/beginner-delegate-program.html

 

 

What is Syntax in Lambda Expression?:

 

A lambda expression has the following form:

 

(parameters) => expression-or-statement-block

 

(a, b) => a + b;   this program

 

(a, b)  èParameter

a+b     è Expression /statement block

=>      è  Lambda Expression

 

You can write Following format also

 

(a, b) =>{ return  a + b }

 

Func ,Action Keyword:

 

Lambda Expression mostly used Func and Action Keyword

  • Func Keyword is one of the generic Delegate

Example 1:

 

Func<int, int,string> Add = (fvalue, svalue) => (fvalue + svalue).ToString();

            MessageBox.Show(Add(3, 5));          // outPut 8

           

Example 2:

 

Func<int, int, int> Add = (fvalue, svalue) => fvalue + svalue;

            MessageBox.Show(Add(3, 5).ToString());          // outPut 8

 

Above program  how its working ?

 

Func  è Func is Keyword

 

Func<int, int,string> è first Two type is parameter ,Last type is return type

 

Add  è Add is Method Name

 

(fvalue, svalue èParameter

 

(fvalue + svalue).ToString(); è Statement

 

 

Other feature:

 

  • You can access outer variable also 

Ex:

 

Int value=50;

 

Func<int, int, int> Add = (fvalue, svalue) => fvalue + svalue+ value;

            MessageBox.Show(Add(3, 5).ToString());          // outPut 58

 

Question ?

 

Int value=50;

 

Func<int, int, int> Add = (fvalue, svalue) => fvalue + svalue+ value;

  

    Int value=100;

 

            MessageBox.Show(Add(3, 5).ToString());  

 

    Int value=200;

 

Post your Answers ….Get Special Gift ….  To Bloger…..

 

 

Action Keyword:

 

Action Type same like Func method but The Action type receives parameters but does not return a parameter. The Func type, however, receives parameters and also returns a result value. The difference is that an Action never returns anything, while the Func always returns something. An Action is a void-style method in the C# language

 

Example:

 

using System;
 
class Program
{
    static void Main()
    {
      // Example Action instances.
      // ... First example uses one parameter.
      // ... Second example uses two parameters.
      // ... Third example uses no parameter.
      // ... None have results.
      Action<int> example1 =
          (int x) => MessageBox.Show("Write {0}", x);
      Action<int, int> example2 =
          (x, y) => MessageBox.Show ("Write {0} and {1}", x, y);
      Action example3 =
          () => MessageBox.Show ("Done");
      // Call the anonymous methods.  Or example1(1)
      example1.Invoke(1);
      example2.Invoke(2, 3);
      example3.Invoke();
    }
}
 
 
 
Output
Write 1
Write 2 and 3
Done
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