Define your own delegate

   

/*
Learning C# 
by Jesse Liberty

Publisher: O'Reilly 
ISBN: 0596003765
*/
 using System;

 namespace DelegatesAndEvents
 {
     class MyClassWithDelegate
     {
         // The delegate declaration.
         public delegate void StringDelegate(string s);

     }

     class MyImplementingClass
     {
         public static void WriteString(string s)
         {
             Console.WriteLine("Writing string {0}", s);
         }

         public static void LogString(string s)
         {
             Console.WriteLine("Logging string {0}", s);
         }

         public static void TransmitString(string s)
         {
             Console.WriteLine("Transmitting string {0}", s);
         }

     }

    public class TesterDelegatesAndEvents
    {
       public void Run()
       {
           // Define three StringDelegate objects.
           MyClassWithDelegate.StringDelegate
               Writer, Logger, Transmitter;

           // Define another StringDelegate
           // to act as the multicast delegate.
           MyClassWithDelegate.StringDelegate
               myMulticastDelegate;

           // Instantiate the first three delegates,
           // passing in methods to encapsulate.
           Writer = new MyClassWithDelegate.StringDelegate(
               MyImplementingClass.WriteString);
           Logger = new MyClassWithDelegate.StringDelegate(
               MyImplementingClass.LogString);
           Transmitter =
               new MyClassWithDelegate.StringDelegate(
               MyImplementingClass.TransmitString);

           // Invoke the Writer delegate method.
           Writer("String passed to Writer
");

           // Invoke the Logger delegate method.
           Logger("String passed to Logger
");

           // Invoke the Transmitter delegate method.
           Transmitter("String passed to Transmitter
");

           // Tell the user you are about to combine
           // two delegates into the multicast delegate.
           Console.WriteLine(
               "myMulticastDelegate = Writer + Logger");

           // Combine the two delegates;  assign the result
           // to myMulticastDelegate
           myMulticastDelegate = Writer + Logger;

           // Call the delegated methods; two methods
           // will be invoked.
           myMulticastDelegate(
               "First string passed to Collector");

           // Tell the user you are about to add
           // a third delegate to the multicast.
           Console.WriteLine(
               "
myMulticastDelegate += Transmitter");

           // Add the third delegate.
           myMulticastDelegate += Transmitter;

           // Invoke the three delegated methods.
           myMulticastDelegate(
               "Second string passed to Collector");

           // Tell the user you are about to remove
           // the Logger delegate.
           Console.WriteLine(
               "
myMulticastDelegate -= Logger");

           // Remove the Logger delegate.
           myMulticastDelegate -= Logger;

           // Invoke the two remaining delegated methods.

           myMulticastDelegate(
               "Third string passed to Collector");
       }

       [STAThread]
       static void Main()
       {
          TesterDelegatesAndEvents t = new TesterDelegatesAndEvents();
          t.Run();
       }
    }
 }