Events in C#

public class Messenger
{
 public delegate void MessageEventHandler(object source, MessageEvent e);

 public event MessageEventHandler changed;

 public void Run()
 {
  fireMessageEvent("Message");
 }

 private void fireMessageEvent(string text)
 {
  log.Info(text);
  if (changed != null)
  {
   changed(this, new MessageEvent(text));
  }
 }
}

public class MessageEvent : EventArgs
{

 private readonly string message;

 public MessageEvent(string message)
 {
  this.message = message;
 }

 public string Message
 {
  get { return this.message; }
 }
}

public class Client
{
 Messenger messenger = new Messenger();

 public Client(){
  messenger.changed += new Messenger.MessengerEventHandler(messenger_changed);
 }

 void messenger_changed(object source, MessageEvent e)
 {
  Console.WriteLine(e.Message);
 }
}