public static void Main()
        {
            Receiver receiver = new Receiver();
            Command command = new ConcreteCommand(receiver);
           
            Invoker aa = new Invoker();

            aa.SetCommand(command);
            aa.ExecuteCommand();           
        }
 public ConcreteCommand(Receiver receiver)
     : base(receiver)
 { 
 }
 public Command(Receiver receiver)
 {
     this.receiver = receiver;
 }