// 观察者模式 定义对象间的一种一对多的依赖关系，当一个对象的状态发生改变时，所有依赖于它的对象都得到通知并自动更新。
static void Observer()
{
INotifyer notifyer = new Secretary();
Observer observer1 = new StockObserver("张三", notifyer);
Observer observer2 = new StockObserver("魏观察", notifyer);
notifyer.Attach(observer1);
notifyer.Attach(observer2);
notifyer.Detach(observer2);
notifyer.NotifyerState = "老板回来了";
notifyer.Notify();
}
static void Main(string[] args)
{
StockGrabber stockGrabber = new StockGrabber();
var stockObserver1 = new StockObserver(stockGrabber);
stockGrabber.setIbmPrice(197.00);
stockGrabber.setaaplPrice(677.60);
stockGrabber.setgoogPrice(676.40);
var stockObserver2 = new StockObserver(stockGrabber);
stockGrabber.setIbmPrice(97.00);
stockGrabber.setaaplPrice(77.60);
stockGrabber.setgoogPrice(76.40);
stockGrabber.Unregister(stockObserver1);
}