C#中的event怎么知道是什么时候调用呢

Question

所谓事件,不就是某些属性改变的时候触发一个方法么
而属性,就是get;set;不仅仅是个Public变量,里面是带方法的

Answer 1

你可以这么定义
        private object _handlerKey = new object();        /// <summary>
        /// 选中项改变事件（需要启用AutoPostBack）
        /// </summary>
        public event EventHandler SelectedIndexChanged
        {
            add
            {
                Events.AddHandler(_handlerKey, value);
            }
            remove
            {
                Events.RemoveHandler(_handlerKey, value);
            }
        }        protected virtual void OnSelectedIndexChanged(EventArgs e)
        {
            EventHandler handler = Events[_handlerKey] as EventHandler;            if (handler != null)
            {
                handler(this, e);
            }
        }      //在需要触发的代码段里去执行
       OnSelectedIndexChanged(EventArgs.Empty);//触发SelectedIndexChanged

Answer 2

你绑定的事件是什么，就通过那个事件触发，比如btn.click+=，就是单击button时触发

Answer 3

    class Program
    {
        static void Main(string[] args)
        {
            Observer ob = new Observer(new Publisher());
            Console.ReadKey();
        }
    }    public class Observer
    {
        private Publisher pub;        public Observer(Publisher pub)
        {
            this.pub = pub;
            pub.SampleEvent += pub_SampleEvent;
        }        void pub_SampleEvent(object sender, SampleEventArgs e)
        {
            Console.WriteLine("The latest message is " + e.Message);
        }
    }    public class Publisher
    {
        private Timer timer;
        public Publisher()
        {
            timer = new Timer((e) => {
                RaiseSampleEvent();
            }, new AutoResetEvent(false),1,1000);
           
        }
        // Declare the delegate (if using non-generic pattern).
        public delegate void SampleEventHandler(object sender, SampleEventArgs e);        // Declare the event.
        public event SampleEventHandler SampleEvent;        // Wrap the event in a protected virtual method
        // to enable derived classes to raise the event.
        protected virtual void RaiseSampleEvent()
        {
            // Raise the event by using the () operator.
            if (SampleEvent != null)
                SampleEvent(this, new SampleEventArgs(DateTime.Now.ToString()));
        }
    }    public class SampleEventArgs : EventArgs
    {
        public string Message;
        public SampleEventArgs(string message)
        {
            Message = message;
        }
    }

Answer 4

思路错误,
实例化event者,并不知道,也不关心这个event什么时候会被触发,
他只需要知道,event如果被触发了,他该干什么(绑上哪些委托)