将一个请求封装为一个对象，从而使你可用不同的请求对客户进行参数化；对请求排队或记录请求日志，以及支持可撤销的操作。
作用：
1、它能较容易地设计一个命令队列；
2、在需要的情况下，可以较容易地将命令记入日志；
3、允许接收请求的一方决定是否要否决请求；
4、可以容易地实现对请求的撤销和重做；
5、由于加进新的具体命令类不影响其他的类，因此增加新的具体命令类很容易。
//基本
//知道如何实施与执行一个与请求相关的操作，任何类都可能作为一个接收者。
class Receiver
{
public void Action()
{
Console.WriteLine("执行请求！");
}
public void Action1()
{
Console.WriteLine("执行请求2！");
}
}
//声明执行操作的接口
abstract class Command
{
protected Receiver receiver;
public Command(Receiver receiver)
{
this.receiver = receiver;
}
abstract public void Execute();
}
//将一个接收者对象绑定于一个动作，调用接收者相应的操作，以实现Execute。
class ConcreteCommand : Command
{
public ConcreteCommand(Receiver receiver) : base(receiver)
{
}
public override void Execute()
{
receiver.Action();
receiver.Action1();
}
}
//要求该命令执行这个请求
class Invoker
{
Command command;
public void SetCommand(Command command)
{
this.command = command;
}
public void ExecuteCommand()
{
command.Execute();
}
}
调用：
Receiver r = new Receiver();
Command c = new ConcreteCommand(r);
Invoker i = new Invoker();
i.SetCommand(c);
i.ExecuteCommand();
//松耦合
//烧肉串者
public class Barbecuer
{
public void BakeMutton() { Console.WriteLine("烧肉串！"); }
public void BakeChickenWing() { Console.WriteLine("烧鸡翅！"); }
}
//抽象命令基类
public abstract class Command
{
protected Barbecuer receiver;
public Command(Barbecuer receiver)
{
this.receiver = receiver;
}
public abstract void ExecuteCommand();
}
//命令基类实现
class BakeChickenWingCommand : Command
{
public BakeChickenWingCommand(Barbecuer receiver) : base(receiver)
{
}
public override void ExecuteCommand()
{
receiver.BakeChickenWing();
}
}
class BakeMuttonCommand : Command
{
public BakeMuttonCommand(Barbecuer receiver) : base(receiver)
{
}
public override void ExecuteCommand()
{
receiver.BakeMutton();
}
}
//服务员类
class Waiter
{
//增加存放具体命令的容器
IList<Command> orders = new List<Command>();
//设置订单
public void SetOrder(Command command)
{
if(command.ToString()== "mlms2.BakeChickenWingCommand")
{
Console.WriteLine("服务员：鸡翅没有了，请点别的烧烤。");
}
else
{
orders.Add(command);
Console.WriteLine("增加订单：" + command.ToString() + " 时间：" + DateTime.Now.ToString());
}
}
//取消订单
public void CancelOrder(Command command)
{
orders.Remove(command);
Console.WriteLine("取消订单：" + command.ToString() + " 时间：" + DateTime.Now.ToString());
}
//通知全部执行
public void Notify()
{
foreach (Command item in orders)
{
item.ExcuteCommand();
}
}
}
m.ExecuteCommand();
}
}
}
调用：
//开店前的准备
Barbecuer person = new Barbecuer();
Command cmd1 = new BakeMuttonCommand(person);
Command cmd2 = new BakeMuttonCommand(person);
Command cmd3 = new BakeChickenWingCommand(person);
Waiter waiter = new Waiter();
//开门营业 顾客点菜
waiter.SetOrder(cmd1);
waiter.SetOrder(cmd2);
waiter.SetOrder(cmd3);
//点菜完毕，通知厨房
waiter.Notify();
waiter.CancelOrder(cmd3);