}

    class MyClass
    {
        //聲明一個(gè)成員變量來(lái)保存事件句柄（事件被激發(fā)時(shí)被調(diào)用的delegate）
        private EventHandler m_Handler = null;

        //激發(fā)事件
        public void FireAEvent()
        {
            if (m_Handler != null)
            {
                m_Handler();
            }
        }

        //聲明事件
        public event EventHandler AEvent
        {
            //添加訪(fǎng)問(wèn)器
            add
            {
                //注意,訪(fǎng)問(wèn)器中實(shí)際包含了一個(gè)名為value的隱含參數(shù)
                //該參數(shù)的值即為客戶(hù)程序調(diào)用+=時(shí)傳遞過(guò)來(lái)的delegate
                Console.WriteLine("AEvent add被調(diào)用,value的HashCode為:" + value.GetHashCode());
                if (value != null)
                {
                    //設(shè)置m_Handler域保存新的handler
                    m_Handler = value;
                }
            }

            //刪除訪(fǎng)問(wèn)器
            remove
            {
                Console.WriteLine("AEvent remove被調(diào)用,value的HashCode為:" + value.GetHashCode());
                if (value == m_Handler)
                {
                    //設(shè)置m_Handler為null,該事件將不再被激發(fā)
                    m_Handler = null;
                }
            }

        }

    }

    class Program
    {
        static void Main(string[] args)
        {
            MyClass obj = new MyClass();
            //創(chuàng)建委托
            EventHandler MyHandler = new EventHandler(MyEventHandler);
            MyHandler += MyEventHandle2;
            //將委托注冊(cè)到事件
            obj.AEvent += MyHandler;
            //激發(fā)事件
            obj.FireAEvent();
            //將委托從事件中撤銷(xiāo)
            obj.AEvent -= MyHandler;
            //再次激發(fā)事件
            obj.FireAEvent();

            Console.ReadKey();
        }

        //事件處理程序
        static void MyEventHandler()
        {
            Console.WriteLine("This is a Event!");
        }

        //事件處理程序
        static void MyEventHandle2()
        {
            Console.WriteLine("This is a Event2!");
        }
    }