主人 猫 老鼠

class cat
    {
        public event EventHandler miao;

        protected virtual void onmiao(EventArgs e)
        {
            if (miao != null)
                miao(this, e);

        }

        public void domiao()
        {
            Console.WriteLine("cat miao");
            onmiao(EventArgs.Empty);
       
        }
   
    }

    class mouse
    {
        public void run(object sender, EventArgs e)
        {
            Console.WriteLine("mouse run..");
       
        }
   
    }
    class owner
    {
        public void noise(object sender, EventArgs e)
        {
            if (sender is cat)
                 Console.WriteLine("heard cat miao..");
            else
                Console.WriteLine("heard mouse noise");
             Console.WriteLine("owner wake...");
        }
   
    }

 class Program
    {
        static void Main(string[] args)
        {

            cat cat = new cat();
            mouse m = new mouse();
            owner o = new owner();
           cat.miao += m.run;
            cat.miao += o.noise;
           cat.domiao();
        }
    }