C# 委托事件简介

简单理解C#委托事件，示例如下所示：

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using System; /// <summary> /// ---------------------委托步骤--------------------- /// 第一步：声明委托 /// 第二步：委托使用方法的实现 /// 第三步：委托的解释(将方法以变量的形式传递，且以方法的形式执行)--方法与委托建立联系 /// 注： /// 委托链的概念(+=、-=,+=表示建立联系，-=表示委托作废) /// 匿名函数：一次性调用(如需多次调用，则应提取) /// /// ---------------------事件：可理解为一种特殊的功能受限的委托--------------------- /// 第一步：声明事件(eg：public static event DelegateSayHello EventSayHello;) /// 第二步：订阅或取消事件(+=/-=) /// 第三步：调用事件 /// </summary> namespace DelegateDemo {     /// <summary>     /// 无参无返回值委托     /// </summary>     public delegate void DelegateSayHello();     /// <summary>     /// 带参无返回值委托     /// </summary>     /// <param name="messageInfo">参数信息</param>     /// <returns></returns>     public delegate string DelegateSayMessage(string messageInfo);     /// <summary>     /// 带参无返回值委托     /// </summary>     /// <param name="messageInfo">参数信息</param>     public delegate void DelegateSayGoodBye(string messageInfo);       class Program     {         //声明事件         public static event DelegateSayMessage EventSayHello;         static void Main(string[] args)         {             string message = DelegateTest();             //Console.WriteLine(message);               //注册事件/订阅事件             EventSayHello += Program_EventSayMessage;             //调用事件             if (EventSayHello != null) Program_EventSayMessage("事件调用来一波");               Console.ReadLine();         }           private static string Program_EventSayMessage(string messageInfo)         {             Console.WriteLine($"{messageInfo}");             return messageInfo;         }           private static string DelegateTest()         {             //委托简单用法             DelegateSayHello say = SayHello;             say();               DelegateSayMessage mes = SayMessage;             string message = mes("带参带返回值");               //委托链用法             DelegateSayHello say1 = SayHello;             say += SayHello;             say -= SayHello;               //匿名函数用法             DelegateSayGoodBye nickMethod = delegate (string messageInfo)             {                 Console.WriteLine($"{messageInfo}我是无参无返回值匿名函数");             };             nickMethod("nickMethod 匿名方法调用==");               DelegateSayMessage returnSay = delegate (string messageInfo)             {                 string str = messageInfo + "有参有返回值匿名函数：";                 Console.WriteLine(str);                 return str;             };             returnSay("returnSay 匿名方法调用==");             //Lamda表达式             DelegateSayGoodBye lamda = (messageInfo) =>             {                 Console.WriteLine($"{messageInfo }lamda用法来一波");             };             lamda("swg:");             return message;         }           private static void SayHello()         {             Console.WriteLine("hello delegate");         }         private static string SayMessage(string messageInfo)         {             string str = "SayMessage==" + messageInfo;             return str;         }     } }