public static void Test()
        {
            Chatroom    c      = new Chatroom();
            Participant George = new BeatleParticipant("George");
            Participant Paul   = new BeatleParticipant("Paul");
            Participant Ringo  = new BeatleParticipant("Ringo");
            Participant John   = new BeatleParticipant("John");
            Participant Yoko   = new NonBeatleParticipant("Yoko");

            c.Register(George);
            c.Register(Paul);
            c.Register(Ringo);
            c.Register(John);
            c.Register(Yoko);

            Yoko.Send("John", "Hi John!");
            Paul.Send("Ringo", "All you need is love");
            Ringo.Send("George", "My sweet Lord");
            Paul.Send("John", "Can't you buy me love");
            John.Send("Yoko", "My sweet love");
        }
  public static void Main(string[] args)
  {
    // Create chatroom
    Chatroom c = new Chatroom();

    // Create 'chatters' and register them
    Participant George =new BeatleParticipant("George");
    Participant Paul = new BeatleParticipant("Paul");
    Participant Ringo = new BeatleParticipant("Ringo");
    Participant John = new BeatleParticipant("John") ;
    Participant Yoko = new NonBeatleParticipant("Yoko");

    c.Register( George );
    c.Register( Paul );
    c.Register( Ringo );
    c.Register( John );
    c.Register( Yoko );

    // Chatting participants
    Yoko.Send( "John", "Hi John!" );
    Paul.Send( "Ringo", "All you need is love" );
    Ringo.Send( "George", "My sweet Lord" );
    Paul.Send( "John", "Can't buy me love" );
    John.Send( "Yoko", "My sweet love" ) ;

  }