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);

Before that what we used Please check this url

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


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;
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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


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)
example2.Invoke(2, 3);


Write 1
Write 2 and 3


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