Delegates

What are Delegates in C# and Explain with Example?

 A delegate is a type that represents references to methods with a particular parameter list and return type. A delegate (known as function pointer in C/C++) is a reference type that invokes single/multiple methods (s) through the delegate instance. It holds a reference to the methods. Whenever we want to create a delegate methods we need to declare with delegate keyword.

What is the use of Delegates?

Suppose if we have multiple methods with the same signature (return type & number of parameters) and want to call all the methods with a 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 the address of a single method like as explained in the example below.

Ex:
using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace SingleDelegate
{
 public delegate int SingleDelegate(int x, int y);

public class DeligateClass
{
 public int Add(int a, int b)

{
return a + b;

}
public int Sub(int a, int b)

{
return a - b;

}

}class Program

{ static void Main(string[] args)
{
 DeligateClass cs = new DeligateClass();

SingleDelegate sd = cs.Add;

int i = sd(8, 6);

Console.WriteLine("Add Result:{0}", i);

SingleDelegate sd1 = cs.Sub;

int j=sd1(8,6);

Console.WriteLine("Sub Result:{0}", j);

Console.ReadLine();
}

}

}
 Multicast Delegates
A multicast delegate is used to hold the address of multiple methods in the single delegate. To hold multiple addresses with delegate we will use overloaded += operator and if we want to remove addresses from delegate we need to use overloaded operator -=
Multicast delegates will work only for the methods which have return type only void. If we want to create a multicast delegate with return type we will get the return type of the last method in the invocation list

Ex:
using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace multicastDeligate
{
 public delegate void Mulitcastdeligate(int x,int y);

public class Delegateclass
{
 public static void Add(int a, int b)

{ Console.WriteLine(a + b);

}
public static void Sub(int a, int b)

{
Console.WriteLine(a - b);

}
public static void Mul(int a, int b)

{
Console.WriteLine(a * b);

}public static void div(int a, int b)

{
Console.WriteLine(a / b);

}

}
class Program

{
static void Main(string[] args)

{
Delegateclass dc = new Delegateclass();

Mulitcastdeligate md = Delegateclass.Add;

md += Delegateclass.Sub;

md += Delegateclass.Mul;

md += Delegateclass.div;

md(8, 4);
Console.ReadLine();

}

}

}