一个简单的小例子让你明白c#中的委托

最新推荐文章于 2025-02-19 14:47:14 发布

最新推荐文章于 2025-02-19 14:47:14 发布 · 82 阅读

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本文通过主持人角色发布问题，多个嘉宾响应的方式，详细解析了C#中事件的实现机制。通过委托链和事件处理，展示了如何利用C#事件进行异步编程和消息传递。文章深入探讨了事件的定义、触发过程以及嘉宾（类）如何响应这些事件，提供了一个全面理解C#事件系统应用的实例。

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模拟主持人发布一个问题，由多个嘉宾来回答这个问题。

分析：从需求中抽出Host (主持人) 类和Guests (嘉宾) 类。

作为问题的发布者，Host不知道问题如何解答。因此它只能发布这个事件，将事件委托给多个嘉宾去处理。因此在Host 类定义事件，在Guests类中定义事件的响应方法。通过多番委托的"+="将响应方法添加到事件列表中，最终 Host 类将触发这个事件。实现过程如下：

代码其实很少下面贴出来所有代码：

QuestionArgs.cs

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usingSystem;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Text;
namespaceEventDemo
{
publicclassQuestionArgs:EventArgs
{
publicstringMessage{get;set;}
}
}

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace EventDemo { public class QuestionArgs:EventArgs { public string Message { get; set; } } }

Program.cs

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usingSystem;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Text;
namespaceEventDemo
{
classProgram
{
staticvoidMain(string[]args)
{
Hosthost=newHost();
host.Name="主持人";
host.args.Message="C#的事件如何实现的？";
Guests[]gArray=newGuests[3]
{
newGuestA(){Name="张小三"},
newGuestB(){Name="李小四"},
newGuestC(){Name="王老五"}
};
//用+=号，将嘉宾的答题方法加入到委托链
host.QuestionEvent+=newQuestionHandler(gArray[0].answer);
host.QuestionEvent+=newQuestionHandler(gArray[1].answer);
host.QuestionEvent+=newQuestionHandler(gArray[2].answer);
//触发事件
host.StartAnswer();
Console.ReadLine();
}
}
}<spanstyle="color:#ff0000;">
</span>

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace EventDemo { class Program { static void Main(string[] args) { Host host = new Host(); host.Name = "主持人"; host.args.Message = "C#的事件如何实现的？"; Guests[] gArray = new Guests[3] { new GuestA(){Name = "张小三"}, new GuestB(){Name = "李小四"}, new GuestC(){Name = "王老五"} }; //用+=号，将嘉宾的答题方法加入到委托链 host.QuestionEvent += new QuestionHandler(gArray[0].answer); host.QuestionEvent += new QuestionHandler(gArray[1].answer); host.QuestionEvent += new QuestionHandler(gArray[2].answer); //触发事件 host.StartAnswer(); Console.ReadLine(); } } }<span style="color:#ff0000;"> </span>

Host.cs

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usingSystem;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Text;
namespaceEventDemo
{
publicdelegatevoidQuestionHandler(objectsender,QuestionArgse);
publicclassHost
{
//定义一个事件
publiceventQuestionHandlerQuestionEvent;
publicQuestionArgsargs{set;get;}
publicHost()
{
//初始化事件参数
args=newQuestionArgs();
}
publicstringName{get;set;}
publicvoidStartAnswer()
{
Console.WriteLine("开始答题");
QuestionEvent(this,args);
}
}
}

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace EventDemo { public delegate void QuestionHandler(object sender,QuestionArgs e); public class Host { //定义一个事件 public event QuestionHandler QuestionEvent; public QuestionArgs args { set; get; } public Host() { //初始化事件参数 args = new QuestionArgs(); } public string Name { get; set; } public void StartAnswer() { Console.WriteLine("开始答题"); QuestionEvent(this, args); } } }

Guests.cs

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usingSystem;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Text;
namespaceEventDemo
{
///<summary>
///父类
///</summary>
publicclassGuests
{
///<summary>
///嘉宾姓名
///</summary>
publicstringName{get;set;}
publicvirtualvoidanswer(objectsender,QuestionArgse)
{
Console.Write("事件的发出者："+(senderasHost).Name);
Console.WriteLine("问题是："+e.Message);
}
}
}

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace EventDemo { /// <summary> /// 父类 /// </summary> public class Guests { /// <summary> /// 嘉宾姓名 /// </summary> public string Name { get; set; } public virtual void answer(object sender, QuestionArgs e) { Console.Write("事件的发出者：" + (sender as Host).Name); Console.WriteLine("问题是：" + e.Message); } } }

GuestC.cs

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usingSystem;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Text;
namespaceEventDemo
{
classGuestC:Guests
{
publicoverridevoidanswer(objectsender,QuestionArgse)
{
base.answer(sender,e);
Console.WriteLine("{0}开始答题：我不知道",this.Name);
}
}
}

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace EventDemo { class GuestC:Guests { public override void answer(object sender, QuestionArgs e) { base.answer(sender, e); Console.WriteLine("{0}开始答题：我不知道", this.Name); } } }

GuestB.cs

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usingSystem;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Text;
namespaceEventDemo
{
classGuestB:Guests
{
publicoverridevoidanswer(objectsender,QuestionArgse)
{
base.answer(sender,e);
Console.WriteLine("{0}开始答题：我不知道",this.Name);
}
}
}

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace EventDemo { class GuestB:Guests { public override void answer(object sender, QuestionArgs e) { base.answer(sender, e); Console.WriteLine("{0}开始答题：我不知道", this.Name); } } }

GuestA.cs

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usingSystem;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Text;
namespaceEventDemo
{
classGuestA:Guests
{
publicoverridevoidanswer(objectsender,QuestionArgse)
{
base.answer(sender,e);
Console.WriteLine("{0}开始答题：我不知道",this.Name);
}
}
}

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace EventDemo { class GuestA:Guests { public override void answer(object sender, QuestionArgs e) { base.answer(sender, e); Console.WriteLine("{0}开始答题：我不知道", this.Name); } } }

运行结果：