Beispiel Listener.cs

using System;

namespace MyCollections
{
   using System.Collections;

	public delegate void ChangedEventHandler (object sender,EventArgs e);

	public class ListWithChangedEvent: ArrayList
	{
     
		public event ChangedEventHandler Changed;

		protected virtual void OnChanged (EventArgs e)
		{
			if (Changed != null)
				Changed (this, e);
		}
      
		public override int Add (object value)
		{
			int i = base.Add (value);
			OnChanged (EventArgs.Empty);
			return i;
		}

		public override void Clear ()
		{
			base.Clear ();
			OnChanged (EventArgs.Empty);
		}

		public override object this [int index] {
			set {
				base [index] = value;
				OnChanged (EventArgs.Empty);
			}
		}
	}
}

namespace TestEvents
{
   using MyCollections;

	class EventListener
	{
		private ListWithChangedEvent List;

		public EventListener (ListWithChangedEvent list)
		{
			List = list;
        
			List.Changed += new ChangedEventHandler (ListChanged);
		}
 
		private void ListChanged (object sender, EventArgs e)
		{
			Console.WriteLine ("This is called when the event fires.");
		}

		public void Detach ()
		{
         
			List.Changed -= new ChangedEventHandler (ListChanged);
			List = null;
		}
	}

	class Test
	{

		public static void Main ()
		{
    
			ListWithChangedEvent list = new ListWithChangedEvent ();

    
			EventListener listener = new EventListener (list);

     
			list.Add ("item 1");
			list.Clear ();
			listener.Detach ();
		}
	}
}