public class Cat
{public delegate void Crying（object sender，EventArgs e）；//定义一个猫叫委托public event Crying cry；//定义猫叫事件public void OnCry（EventArgs e）{if（cry！=null）{cry（this，e）；}}public void StartCrying()//猫叫、触发cry事件{MessageBox.Show("猫开始叫了......");EventArgs e=new EventArgs();OnCry(e);}
}

public class Mouse
{public delegate void Runing（Object sender，EventArgs e）；public evnet delegate run；public void OnRun（EventArgs e）{if(run!=null){run(this,e); }}public void StartRuning(Cat c){c.cry+=new Cat.Crying(c_Cry);//注册了猫叫事件，老鼠听到猫叫则开始逃跑}public void c_Cry(object sender,EvnetArgs e)//老鼠在逃跑时又触发了人被惊醒事件{MessageBox.Show("老鼠开始逃跑了........");EventArgs e=new EventArgs();OnRun(e);}
}
public class Person
{public void Waking(Mouse m){m.run+=new Mouse.Runing(m_run);//人注册了老鼠逃跑事件，老鼠逃跑时人被 惊醒}public void m_run(object sender,EventArgs e){MessageBox.Show("人醒了，What's wrong?");}
}

BtnTest_Click(object sender, EventArgs e)
{Cat c=new Cat();Mouse m=new Mouse();Person p=new Person();m.StartRunning(c);p.Waking(m);c.StartCrying();
}

public interface Observer
{void Response();//对被观察对象的行为作出反应，这里是指猫叫
}
public interface Subject
{void AddObserver(Observer obj);//添加所有的观察者，在发生动作时对他们进行通知
}

public class Cat：Subject
{ArrayList arrlyList；public Cat（）{arrlyList=new ArrayList();}void AddObserver(Observer obj)//实现添加观察着对象的方法{arrlyList.Add(obj);}void Cry()//猫叫了，并通知所有的观察者，作出相应的反应{MessageBox.Show("猫叫了......");foreach(Observer obj in arrlyList){obj.Response();}}
}

public class Mouse：Observer
{public Mouse（Cat c）//将当前的观察着对象添加到观察者集合中{c.AddObserver(this);}public void Response（）{MessageBox.show("老鼠开始逃跑了.....");}
}

public class People:Observer
{public People（Cat c）//将当前的观察着对象添加到观察者集合中{c.AddOberver(this);}public void Respone（）{MessageBox.Show("人醒了，What's Wrong?");}
}

Btn_Click(Object sender,EventArgs e){
Cat c=new Cat();
Mouse m=new Mouse(c);
People p=new People(c);
c.Cry();}