C# Multicast Delegates

In this chapter you will learn:

What are Multicast Delegates
Syntax for Multicast Delegates
Example for Multicast Delegates
Subtract delegate
Use new operator to create delegate

Description

All delegate instances have multicast capability.

Syntax

This means that a delegate instance can reference not just a single target method, but also a list of target methods.

The + and += operators combine delegate instances.

For example:


SomeDelegate d = SomeMethod1;
d += SomeMethod2;

The last line is functionally the same as:

d = d + SomeMethod2;

Invoking d will now call both SomeMethod1 and SomeMethod2. Delegates are invoked in the order they are added.

The - and -= operators remove the right delegate operand from the left delegate operand. For example:

d -= SomeMethod1;

Invoking d will now cause only SomeMethod2 to be invoked.

Example

Example for Multicast Delegates


using System;/*  w  ww . ja  va2s  . co  m*/

delegate void Printer(int i);
class Test
{
    static void consolePrinter(int i)
    {
        Console.WriteLine(i);
    }

    static void consolePrinter2(int i)
    {
        Console.WriteLine("second:" + i);
    }

    static void Main()
    {
        Printer p = consolePrinter;
        p += consolePrinter2;

        p(1);

    }
}

The output:

The delegates are called in the sequence of adding.

Example 2

We can subtract delegate method as well.


using System;/*  w  w w.  ja  v  a  2s.  c o  m*/

delegate void Printer(int i);
class Test
{

    static void consolePrinter(int i)
    {
        Console.WriteLine(i);
    }

    static void consolePrinter2(int i)
    {
        Console.WriteLine("second:" + i);
    }

    static void Main()
    {
        Printer p = consolePrinter;
        p += consolePrinter2;
        p -= consolePrinter;
        p(1);

    }
}

The code above generates the following result.

Example 3


using System;//  w  ww . j  a  v a  2  s. c  o  m

class MainClass
{
  delegate int MyDelegate(string s);
  static void Main(string[] args)
  {
    string MyString = "Hello World";

    
    MyDelegate Multicast = null;

    Multicast += new MyDelegate(DoSomething);
    Multicast += new MyDelegate(DoSomething2);

    Multicast(MyString);
  }

  static int DoSomething(string s)
  {
    Console.WriteLine("DoSomething");
    
    return 0;
  }
  static int DoSomething2(string s)
  {
      Console.WriteLine("DoSomething2");
    return 0;
  }
}

The code above generates the following result.

Next chapter...

What you will learn in the next chapter:

Home »
  C# Tutorial »
    C# Types »
      C# Delegate

C# Delegate

C# Multicast Delegates

delegate parameters
C# Generic delegate
C# Func and Action
C# Anonymous delegate