设计模式面对面之命令模式

public interface IReceiver  {

        void Operation();
    }//end IReceiver

public class ReceiverA : IReceiver {

        public ReceiverA(){

        }

        public void Operation(){
            Console.WriteLine("由ReceiverA处理");
        }

    }//end ReceiverA

public class ReceiverB : IReceiver {

        public ReceiverB(){

        }

        public void Operation(){
            Console.WriteLine("由ReceiverB处理");
        }

    }//end ReceiverB

public interface ICommand  {

        void Execute();
    }//end ICommand

public class CommandRealizeA : ICommand {

        private readonly IReceiver _receiver;

        public CommandRealizeA(){
            _receiver=new ReceiverA();
        }

        public void Execute(){
            _receiver.Operation();
        }

    }//end CommandRealizeA

public class CommandRealizeB : ICommand {

        private readonly IReceiver _receiver;

        public CommandRealizeB()
        {
            _receiver=new ReceiverB();
        }

        public void Execute(){
            _receiver.Operation();
        }

    }//end CommandRealizeB

public class Invoker {

        private ICommand _command;

        public Invoker(){
            _command=new CommandRealizeA();//默认指令
        }

        public void Invoke()
        {
            _command.Execute();
        }

        /// 
        /// <param name="command"></param>
        public void SetCommand(ICommand command)
        {
            _command = command;
        }

    }//end Invoker