C#中的事件介绍

   public  event  delTest  eventTest;

   eventTest += new delTest(method2);

namespace EventDemo
{
    /// <summary>
    /// 发布事件的类
    /// </summary>
    public class TestEventSource
    {
        //定义事件参数类
        public class TestEventArgs : EventArgs
        {
            public readonly char KeyToRaiseEvent;
            public TestEventArgs(char keyToRaiseEvent)
            {
                KeyToRaiseEvent = keyToRaiseEvent;
            }
        }
        //定义delegate
        public delegate void TestEventHandler(object sender, TestEventArgs e);
        //用event 关键字声明事件对象
        public event TestEventHandler TestEvent;
        //事件触发方法
        protected virtual void OnTestEvent(TestEventArgs e)
        {
            if (TestEvent != null)
                TestEvent(this, e);
        }
        //引发事件
        public void RaiseEvent(char keyToRaiseEvent)
        {
            TestEventArgs e = new TestEventArgs(keyToRaiseEvent);
            OnTestEvent(e);
        }
    }
}

namespace EventDemo
{
    /// <summary>
    /// 监听事件的类
    /// </summary>
    public class TestEventListener
    {
        //定义处理事件的方法，他与声明事件的delegate具有相同的参数和返回值类型
        public void KeyPressed(object sender, TestEventSource.TestEventArgs e)
        {
            Console.WriteLine("发送者：{0}，所按得健为：{1}", sender, e.KeyToRaiseEvent);
        }
        //订阅事件
        public void Subscribe(TestEventSource evenSource)
        {
            evenSource.TestEvent += new TestEventSource.TestEventHandler(KeyPressed);
        }
        //取消订阅事件
        public void UnSubscribe(TestEventSource evenSource)
        {
            evenSource.TestEvent -= new TestEventSource.TestEventHandler(KeyPressed);
        }
    }
}

namespace EventDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            //创建事件源对象
            TestEventSource es = new TestEventSource();
            //创建监听对象
            TestEventListener el = new TestEventListener();
            //订阅事件
            Console.WriteLine("订阅事件\n");
            el.Subscribe(es);
            //引发事件
            Console.WriteLine("输入一个字符，再按enter键");
            string s = Console.ReadLine();
            es.RaiseEvent(s.ToCharArray()[0]);
            //取消订阅事件
            Console.WriteLine("\n取消订阅事件\n");
            el.UnSubscribe(es);
            //引发事件
            Console.WriteLine("输入一个字符，再按enter健");
            s = Console.ReadLine();
            es.RaiseEvent(s.ToCharArray()[0]);
        }
    }
}

   del += Sub;   del = del + Sub;

   del += Mul;

   del -= Mul;

        {

           PlayOver(this, null);

        }

            p.PlayOver += new PlayOverEventHandler(p_PlayOver);

            p.Play();