C#事件回调委托EventHandler

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C#预定义了一个事件委托EventHandler，定义如下:

// Summary:
    //     Represents the method that will handle an event.
    //
    // Parameters:
    //   sender:
    //     The source of the event.
    //
    //   e:
    //     An System.EventArgs that contains the event data.
    //
    // Type parameters:
    //   TEventArgs:
    //     The type of the event data generated by the event.
    [Serializable]
    public delegate void EventHandler<TEventArgs>(object sender, TEventArgs e);

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可以看出委托EventHandler其实是一个泛型委托，返回值为void，有两个参数，第二个参数为泛型TEventArgs

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如果我们的事件回调函数返回值类型为void,那么就可以用委托EventHandler来实现事件回调了，代码如下：

using System;using System.Collections.Generic;using System.Text;namespace TestApp{    class Program    {        public static void Main(string[] args)        {            Test tst = new Test();            tst.InitAddEvent(AddEvent); // 传递事件处理函数地址            tst.CallAddEvent();         // 触发事件            Console.Read(); // 暂停程序        }        // 加法事件        public static void AddEvent(object sender, EventArgs e)        {            AddEventData ad = (AddEventData)e;            int c = ad.a + ad.b;            Console.WriteLine("触发事件AddEvent, a+b={0}", c);        }    }    public class Test    {        // 事件对象        private event EventHandler<AddEventData> OnAddEvent;        // 初始化事件        public void InitAddEvent(EventHandler<AddEventData> addEvent)        {            //this.OnAddEvent = addEvent;               this.OnAddEvent += new EventHandler<AddEventData>(addEvent);        }        // 触发事件        public void CallAddEvent()        {            if (OnAddEvent != null)            {                AddEventData ad = new AddEventData();                ad.a = 1;                ad.b = 2;                OnAddEvent(this, ad);            }        }    }    // 事件参数,必须继承类EventArgs    public class AddEventData:EventArgs    {        public int a;        public int b;    }}

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