A delegate in C# language allows us to reference a method. The other way to say this delegate is a function pointer. The function pointer is same as we have pointer to an address now in this case we have pointer to a method address. There are two types of delegates :-

• Single-Cast Delegate:- Here the delegate will refer to or point to single method or we can Say that the pointer is to single method from the delegate.


• Multi-Cast Delegate:-In the multi-cast delegate, the delegate refer to or point to more than One method at runtime.

Delegates features:

• Delegate is a function pointer.


• Delegate declaration is same as method declaration, except they have delegate modifier in front of it.


• The method that a delegate refers or pointing to must have same signature as of delegate method.


• To use a delegate, we have to create the instance of the delegate and pass the method that it is pointing too or referring to.


• Invoke (), This method can be used to invoke the delegate.

The delegates can be declared by adding a delegate keyword in front of any method. For Example- delegate void Mydelegate();

Note:- This is declaration of the delegate and it specifies the method signature that it is pointing or referring. This means the signature of the method that a delegate pointing has no parameter and will not return any thing. But this is an example and we can say the delegate can refer to any type of method.

Example: Demonstrate Delegates

ClsDelegate13.cs

using System;

using System.Collections.Generic;

using System.Text;

namespace cSHARPEXAMPLES

{

  class ClsDelegate13

    {

    delegate void Mydelegate ();

    static String str = "" ;

    static String sd = "" ;

    public String singlecastfx()

        {

          sd = "" ;

          sd = "Single Cast Delegate ==> " ;

          Mydelegate d = null ;

          d += new Mydelegate (singlecastdelegatefx);

          d.Invoke();

          sd = sd + " :: appender" ;

    return sd;

        }

    public String multicastfx() {

          str = "" ;

          str = "starting Value ==> " ;

          Mydelegate d = null ;

          d += new Mydelegate (firstfx);

          d += new Mydelegate (secondfx);

          d();

          str = str + " :: appender" ;

      return str;

          }

    public void firstfx()

        {

          str = str + " :: firstfx" ;

        }

    public void secondfx()

        {

          str = str + " :: secondfx" ;

        }

    public void singlecastdelegatefx()

        {

          sd = sd + " ::singlecastdelegatefx" ;

        }

    }

}

Form13.cs

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

namespace cSHARPEXAMPLES

{

public partial class Form13 : Form

{

  public Form13()

    {

        InitializeComponent();

    }

  private void button1_Click( object sender, EventArgs e)

    { //Multi-cast delegate

      ClsDelegate13 objDelegate = new ClsDelegate13 ();

    MessageBox .Show(objDelegate.multicastfx());

    }

  private void button2_Click( object sender, EventArgs e)

    { //Single-cast delegate

      ClsDelegate13 objDelegate = new ClsDelegate13 ();

    MessageBox .Show(objDelegate.singlecastfx());

    }

  }

}

Output:

Clicking On: Single-cast Delegate Button

Clicking On: Mutil-cast Delegate Button