//Demo1:Declaring an event in an interface and implementing it in //a class.// event_keyword.csusing System;public delegate void MyDelegate();   // delegate declarationpublic interface I {   event MyDelegate MyEvent;   void FireAway();}public class MyClass: I {   public event MyDelegate MyEvent;   public void FireAway()    {      if (MyEvent != null)         MyEvent();   }}public class MainClass {   static private void f()    {      Console.WriteLine("This is called when the event fires.");   }   static public void Main ()    {      I i = new MyClass();      i.MyEvent += new MyDelegate(f);      i.FireAway();   }}

//Demo2:One use for accessor-declarations is to expose a large //number of events without allocating a field for each event, but //instead using a hash table to store the event instances. This is //only useful if you have a very large number of events, but you //expect most of the events will not be implemented.// event_keyword2.csusing System;using System.Collections;public delegate void MyDelegate1(int i);public delegate void MyDelegate2(string s);public delegate void MyDelegate3(int i, object o);public delegate void MyDelegate4();public class PropertyEventsSample {   private Hashtable eventTable = new Hashtable();   public event MyDelegate1 Event1    {      add       {         eventTable["Event1"] = (MyDelegate1)eventTable["Event1"] + value;      }      remove      {         eventTable["Event1"] = (MyDelegate1)eventTable["Event1"] - value;       }   }   public event MyDelegate1 Event2    {      add       {         eventTable["Event2"] = (MyDelegate1)eventTable["Event2"] + value;      }      remove      {         eventTable["Event2"] = (MyDelegate1)eventTable["Event2"] - value;       }   }   public event MyDelegate2 Event3    {      add       {         eventTable["Event3"] = (MyDelegate2)eventTable["Event3"] + value;      }      remove      {         eventTable["Event3"] = (MyDelegate2)eventTable["Event3"] - value;       }   }   public event MyDelegate3 Event4    {      add       {         eventTable["Event4"] = (MyDelegate3)eventTable["Event4"] + value;      }      remove      {         eventTable["Event4"] = (MyDelegate3)eventTable["Event4"] - value;       }   }   public event MyDelegate3 Event5    {      add       {         eventTable["Event5"] = (MyDelegate3)eventTable["Event5"] + value;      }      remove      {         eventTable["Event5"] = (MyDelegate3)eventTable["Event5"] - value;       }   }   public event MyDelegate4 Event6    {      add       {         eventTable["Event6"] = (MyDelegate4)eventTable["Event6"] + value;      }      remove      {         eventTable["Event6"] = (MyDelegate4)eventTable["Event6"] - value;       }   }}public class MyClass {   public static void Main()    {   }}

//Deom3public class SampleEventArgs    {        public SampleEventArgs(string s) { Text = s; }        public String Text {get; private set;} // readonly    }    public class Publisher    {        // Declare the delegate (if using non-generic pattern).        public delegate void SampleEventHandler(object sender, SampleEventArgs e);        // Declare the event.        public event SampleEventHandler SampleEvent;        // Wrap the event in a protected virtual method        // to enable derived classes to raise the event.        protected virtual void RaiseSampleEvent()        {            // Raise the event by using the () operator.            if (SampleEvent != null)                SampleEvent(this, new SampleEventArgs("Hello"));        }    }