c# - 委托(delegate)和事件

Question

我创建了一个非常简单的虚拟程序来理解委托(delegate)和事件。在我下面的程序中，我很简单地调用了一个方法。当我调用一个方法时，在委托(delegate)和事件的帮助下会自动调用五个方法。

请看看我的程序，让我知道哪里错了哪里对，因为这是我第一次使用委托(delegate)和事件。

using System;

namespace ConsoleApplication1
{
    public delegate void MyFirstDelegate();

    class Test
    {
        public event MyFirstDelegate myFirstDelegate;

        public void Call()
        {
            Console.WriteLine("Welcome in Delegate world..");
            if (myFirstDelegate != null)
            {
                myFirstDelegate();
            }
        }        
    }

    class AttachedFunction
    {
        public void firstAttachMethod()
        {
            Console.WriteLine("ONE...");
        }
        public void SecondAttachMethod()
        {
            Console.WriteLine("TWO...");
        }
        public void thirdAttachMethod()
        {
            Console.WriteLine("THREE...");
        }
        public void fourthAttachMethod()
        {
            Console.WriteLine("FOUR...");
        }
        public void fifthAttachMethod()
        {
            Console.WriteLine("FIVE...");
        }
    }

    class MyMain
    {
        public static void Main()
        {
            Test test = new Test();
            AttachedFunction attachedFunction = new AttachedFunction();
            test.myFirstDelegate += new MyFirstDelegate(attachedFunction.firstAttachMethod);
            test.myFirstDelegate += new MyFirstDelegate(attachedFunction.SecondAttachMethod);
            test.myFirstDelegate += new MyFirstDelegate(attachedFunction.thirdAttachMethod);
            test.myFirstDelegate += new MyFirstDelegate(attachedFunction.fourthAttachMethod);
            test.myFirstDelegate += new MyFirstDelegate(attachedFunction.fifthAttachMethod);

            test.Call();
            Console.ReadLine();
        }
    }
}

Answer 1

事件是使用委托(delegate)来实现的。也就是说，按照惯例，事件采取以下形式:

 void EventHandler(Object sender, EventArgs args);

EventHandler实际上是.Net 中定义的委托(delegate)。 EventArgs 是 .Net 中的一个类，用作传递附加信息的占位符。如果您有额外的信息，您将创建一个派生自 EventArgs 并包含额外数据属性的类；因此，您可以像这样创建自己的委托(delegate):

void MyEventHandler(Object sender, MyEventArgs args);

Microsoft 有一个关于事件的教程 here还描述了定义和引发事件 here