Mediator

// Mediator pattern -- Real World example

using System; using System.Collections; namespace DoFactory.GangOfFour.Mediator.RealWorld {       // MainApp test application    class MainApp   {      static void Main()     {        // Create chatroom       Chatroom chatroom = new Chatroom();        // Create participants and register them       Participant George = new Beatle("George");       Participant Paul = new Beatle("Paul");       Participant Ringo = new Beatle("Ringo");       Participant John = new Beatle("John") ;       Participant Yoko = new NonBeatle("Yoko");       chatroom.Register(George);       chatroom.Register(Paul);       chatroom.Register(Ringo);       chatroom.Register(John);       chatroom.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") ;        // Wait for user       Console.Read();     }   }    // "Mediator"    abstract class AbstractChatroom   {      public abstract void Register(Participant participant);      public abstract void Send(        string from, string to, string message);   }    // "ConcreteMediator"    class Chatroom : AbstractChatroom   {      private Hashtable participants = new Hashtable();      public override void Register(Participant participant)     {        if (participants[participant.Name] == null)       {         participants[participant.Name] = participant;       }       participant.Chatroom = this;     }      public override void Send(        string from, string to, string message)     {       Participant pto = (Participant)participants[to];        if (pto != null)       {         pto.Receive(from, message);       }     }   }    // "AbstractColleague"    class Participant   {      private Chatroom chatroom;      private string name;      // Constructor      public Participant( string name)     {        this.name = name;     }      // Properties      public string Name     {        get{ return name; }     }      public Chatroom Chatroom     {        set{ chatroom = value; }        get{ return chatroom; }     }      public void Send( string to, string message)     {       chatroom.Send(name, to, message);     }      public virtual void Receive(        string from, string message)     {       Console.WriteLine("{0} to {1}: '{2}'",         from, Name, message);     }   }    //" ConcreteColleague1"    class Beatle : Participant   {      // Constructor      public Beatle( string name) : base(name)     {     }      public override void Receive( string from, string message)     {       Console.Write("To a Beatle: ");        base.Receive(from, message);     }   }    //" ConcreteColleague2"    class NonBeatle : Participant   {      // Constructor      public NonBeatle( string name) : base(name)     {     }      public override void Receive( string from, string message)     {       Console.Write("To a non-Beatle: ");        base.Receive(from, message);     }   } }