public void TestCase6()
        {
            Receiver receiver = new Receiver();
              Command cmd = new ConcreteCommand(receiver, "Hello World");

              Invoker invoker = new Invoker();
              invoker.StoreCommand(cmd);

              invoker.Invoke();
              invoker.UndoInvoke();
        }
 public ConcreteCommand(Receiver receiver, string state)
 {
     _receiver = receiver;
       _state = state;
 }