使用事件属性， 优化事件实现

       Events 属性的类型为 EventHandlerList；
private static readonly object ClickEvent = new object();
      
            public event EventHandler Click
      {
                 add
         {
            Events.AddHandler(ClickEvent, value);
         }
                  remove
         {
            Events.RemoveHandler(ClickEvent, value);
         }
      }