C# : Multicast delegates : Part 15

• A delegate pointing to more than one function is called Multicast Delegate.
• When this delegate is invoked all the functions pointing to are invoked.
• If the delegate has return type other than void and if the delgate is multicast delegate than only the value of last invoked method will be returned.
• Multicast delegate makes observer design pattern very simple.
• Multicast delegate can be created by two ways
• =
• +=
• In multicast delegate all the method assigned to delegate should have same signature (return type).

Example

 namespace DelegatesMulticast  
 {  
   class Program  
   {  
     public delegate void PrintDelegate();  
     static void Main(string[] args)  
     {  
       //Approach 1  
       Console.WriteLine("Approach 1 '='");  
       PrintDelegate del1, del2, del3, del4;  
       del1 = new PrintDelegate(Print1);  
       del2 = new PrintDelegate(Print2);  
       del3 = new PrintDelegate(Print3);  
       del4 = del1 + del2 + del3;  
       del4();  
       //Approach 2  
       Console.WriteLine("Approach 2 '+='");  
       PrintDelegate del = new PrintDelegate(Print1);  
       del += Print2;  
       del += Print3;  
       del();  
     }  
     public static void Print1()  
     {  
       Console.WriteLine("Invoked from Method 1");  
     }  
     public static void Print2()  
     {  
       Console.WriteLine("Invoked from Method 2");  
     }  
     public static void Print3()  
     {  
       Console.WriteLine("Invoked from Method 3");  
     }  
   }  
 }  

Output