What is Delegates in C# and Use of Delegates in C#?

Question

Here I will explain what is delegates in c#.net with example. Basically delegates in c# are type safe objects which are used to hold reference of one or more methods in c#.net. Delegates concept will match with pointer concept of c language.

Whenever we want to create delegate methods we need to declare with delegate keyword and delegate methods signature should match exactly with the methods which we are going to hold like same return types and same parameters otherwise delegate functionality won’t work if signature not match with methods.

 

Syntax of Delegate & Methods Declaration

public delegate int Delegatmethod(int a,int b);

public class Sampleclass

{

public int Add(int x, int y)

{

return x + y;

}

public int Sub(int x, int y)

{

return x + y;

}

}

 

If you observe above code I declared Delegatmethod method with two parameters which matching with methods declared in Sampleclass class.

 

Complete Example

public delegate int DelegatSample(int a,int b);

public class Sampleclass

{

public int Add(int x, int y)

{

return x + y;

}

public int Sub(int x, int y)

{

return x - y;

}

}

class Program

{

static void Main(string[] args)

{

Sampleclass sc=new Sampleclass();

 

DelegatSample delgate1 = sc.Add;

int i = delgate1(10, 20);

Console.WriteLine(i);

DelegatSample delgate2 = sc.Sub;

int j = delgate2(20, 10);

Console.WriteLine(j);

}

}

Output

Add Result : 30

Sub Result : 10

 

What is the use of Delegates?

 

Suppose if you have multiple methods with same signature (return type & number of parameters) and want to call all the methods with single object then we can go for delegates.

 

Delegates are two types

 

      -   Single Cast Delegates

      -  Multi Cast Delegates

 

Single Cast Delegates

 

Single cast delegate means which hold address of single method like as explained in above example.

 

Multicast Delegates

 

Multi cast delegate is used to hold address of multiple methods in single delegate. To hold multiple addresses with delegate we will use overloaded += operator and if you want remove addresses from delegate we need to use overloaded operator -=

 

Syntax of Multicast Delegate & Method Declaration

public delegate void MultiDelegate(int a,int b);

public class Sampleclass

{

public static void Add(int x, int y)

{

Console.WriteLine("Addition Value: "+(x + y));

}

public static void Sub(int x, int y)

{

Console.WriteLine("Subtraction Value: " + (x - y));

}

public static void Mul(int x, int y)

{

Console.WriteLine("Multiply Value: " + (x * y));

}

}

if you observe above code I declared MultiDelegate method with void return type.

Complete Example

 

public delegate void MultiDelegate(int a,int b); public class Sampleclass { public static void Add(int x, int y) { Console.WriteLine("Addition Value: "+(x + y)); } public static void Sub(int x, int y) { Console.WriteLine("Subtraction Value: " + (x - y)); } public static void Mul(int x, int y) { Console.WriteLine("Multiply Value: " + (x * y)); } } class Program { static void Main(string[] args) { Sampleclass sc=new Sampleclass(); MultiDelegate del = Sampleclass.Add; del += Sampleclass.Sub; del += Sampleclass.Mul; del(10, 5); Console.ReadLine(); } }

 

Output: Whenever we run above code we will get output like as shown below

Addition Value:15

Subtraction Value: 5

Multiply Value:50