观察者模式

interface ISubject
{
    void registerInterest(IObserver ob);
}

interface IObserver
{
    void Update();
}

public class Subject : ISubject
{
    ArrayList al = new ArrayList();

    public void registerInterest(IObserver ob)
    {
          al.Add(ob);
     }

     void sendNotify()
     {
            foreach(IObserver ob in al)
            {
                  ob.Update();
             }
      }

     void xxxxxxxxxxx()
     {
            sendNotify();
      }
}

public class AObserver
{
    public void Update()
    {

     }
}

public class BObserver
{
    public void Update()
    {

     }
}

public static void Main()
{
       .......

}