c#的事件实现的原理

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如果你看了本BLOG写的委托的文章，理解本文应该比较容易，C#中的事件的实现是通过委托直接实现的，所以本文只给出事件实现的代码示例，如果你明白了委托，相信看懂本代码应该不难。

using System;
namespace Events
{
        delegate void SomeDelegate(string sender);
        interface ISomeInterface
        {
                event SomeDelegate SomeEvent;
                void PerformSomeEvent();
                void SomeEventHandler(string sender);
        }
        abstract class AbstractClass:ISomeInterface
        {
                public virtual event SomeDelegate SomeEvent;
                public abstract void SomeEventHandler(string sender);
                public abstract void  PerformSomeEvent();
                protected void PerformSomeEventInternal(string sender)
                {
                        if(null!=SomeEvent)
                        {
                                SomeEvent(sender);
                         }
                 }
                protected void SomeEventHandlerInternal(string sender,string receiver)
                {
                        Console.WriteLine("some event has been handler");
                        Console.WriteLine(" Sender is ["+ sender+"]");
                        Console.WriteLine("Receiver is ["+receiver+"]");
                        Console.WriteLine("------------------------------------");
                 }
         }
        class SomeClass:AbstractClass,ISomeInterface
        {
                public override void PerformSomeEvent()
                {
                        PerformSomeEventInternal("Some Class");
                }
                public override void SomeEventHandler(string sender)
                {
                        SomeEventHandlerInternal(sender,"Some Class");
                 }
        }
        class AnotherClass:AbstractClass,ISomeInterface
        {
                public override void PerformSomeEvent()
                {
                        PerformSomeEventInternal("Another Class");
                }
                public override void SomeEventHandler(string sender)
                {
                        SomeEventHandlerInternal(sender,"Another Class");
                 }
        }
        class SomeApplication
        {
                public static void SomeEventStaticHander(string sender)
                {
                        Console.WriteLine("some event has been handler.");
                        Console.WriteLine(" Sender is ["+ sender+"]");
                        Console.WriteLine("Receiver is [some application]");
                        Console.WriteLine("-------------------------------------");
                 }
                static void Main(string [] args)
                {
                        SomeClass someclass=new SomeClass();
                        AnotherClass anotherclass=new AnotherClass();
                        someclass.SomeEvent+=new SomeDelegate(someclass.SomeEventHandler);
                        someclass.SomeEvent+=new SomeDelegate(anotherclass.SomeEventHandler);
                        someclass.SomeEvent+=new SomeDelegate(SomeApplication.SomeEventStaticHander);
                        someclass.PerformSomeEvent();
                        Console.ReadLine();
                 }
         }
}

运行的结果截图：