Simple and Multicast Delegate in C#

A useful property of delegate objects is that multiple objects can be assigned to one delegate instance by using the + operator. The multicast delegate contains a list of the assigned delegates. When the multicast delegate is called, it invokes the delegates in the list, in order. Only delegates of the same type can be combined.

The "-" operator can be used to remove a component delegate from a multicast delegate.

1. Open Visual Studio go to>>File>>New>>Website>>Asp.net Empty Website and name anything but named DelegatesExplained:

 

2. Add New WebForm to your Project and Name DelegateExplained.aspx,you can name anything:



3. Add the following under the body tag of Desing page of DelegatesExplained.aspx:

<form id="form1" runat="server">
    <div>

    <asp:Label ID="Label1" runat="server"></asp:Label>
    <asp:Label ID="Label2" runat="server"></asp:Label>
    <asp:Label ID="Label3" runat="server"></asp:Label>

    </div>
    </form>

4. Now open .DelegatedExplained.cs and define the delegate name Delegates:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;


public delegate void Delegates();

5. Create three functions name First,Second and Third outside the pageload() function:

protected void Page_Load(object sender, EventArgs e)
{

}
public void First()
{
    Label1.Text = "First";
}

public void Second()
{
    Label2.Text = "Second";
}

public void Third()
{
    Label3.Text = "Third";
}

6. Create Objects Of Delegate under pageload() method:

protected void Page_Load(object sender, EventArgs e)
{
    MultipleDelegate m1,m2,m3;
}
public void First()
{
    Label1.Text = "First";
}

public void Second()
{
    Label2.Text = "Second";
}

public void Third()
{
    Label3.Text = "Third";
}

 7. Now add refrence of Function name First() to m1 and calling the function by calling m1():

protected void Page_Load(object sender, EventArgs e)
{
    MultipleDelegate m1;

    m1 = First;  //adding reference to the First Function
    m2=Second;   //adding reference to the SecondFunction
    m3=Third;  //adding reference to the Third Function
    m1();
    m2();
    m3();
}
public void First()
{
    Label1.Text = "First";
}

public void Second()
{
    Label2.Text = "Second";
}

public void Third()
{
    Label3.Text = "Third";
}

Now run by pressing ctrl+f5;

 

 Now see output will be:

 

 

Now Multicast Delegates by using + operator  rather then calling each object separately create a new object m4 and add all the delegates objects in it.

 

 Only delegates of the same type can be combined.

   protected void Page_Load(object sender, EventArgs e)
   {
       MultipleDelegate m1, m2, m3,m4;

       m1 = First;  //adding reference to the First Function

       m2 = Second;   //adding reference to the SecondFunction

       m3 = Third;  //adding reference to the Third Function

       m4 = m1 + m2 + m3;   //casting all three objects of MuticastDelegate to one object;

       m4();
   }
   public void First()
   {
       Label1.Text = "First";
   }

   public void Second()
   {
       Label2.Text = "Second";
   }

   public void Third()
   {
       Label3.Text = "Third";
   }

 Now see output will be the same:

 

 

You Can also use the "-" operator to remove any object as given below:

Create new object m5:

   protected void Page_Load(object sender, EventArgs e)
   {
       MultipleDelegate m1, m2, m3,m4,m5;

       m1 = First;  //adding reference to the First Function

       m2 = Second;   //adding reference to the SecondFunction

       m3 = Third;  //adding reference to the Third Function

       m4 = m1 + m2 + m3;   //casting all three objects of MuticastDelegate to one object;

       m5 = m4 - m3;

       m5();
   }
   public void First()
   {
       Label1.Text = "First";
   }

   public void Second()
   {
       Label2.Text = "Second";
   }

   public void Third()
   {
       Label3.Text = "Third";
   }

Now output will change and show only two functions: First and Second:

 

 

Thanks.