具有类继承的EventArgs但我不明白它有用吗？

I don't understand how extending EventArgs is useful.

我不明白扩展EventArgs是如何有用的。

public class ClickedEventArgs : EventArgs {
  int x;
  int y;
  public ClickedEventArgs (int x, int y) { 
   this.x = x; 
   this.y = y; 
  }
  public int X { get { return x; } } 
  public int Y { get { return y; } } 
}

Code is above. How can i use this inheritance?Also; i want to learn how can i call this code blog from default.aspx

代码在上面。我怎样才能使用这种继承呢?我想学习如何从default.aspx调用此代码博客

3 个解决方案

#1

Are you asking why it's useful to derive from EventArgs in the first place? I have to say that with C# 1 it didn't make a lot of sense, because of the way delegate conversion worked - but as of C# 2 it's more sensible. It allows an event handler to be registered with an event even if it doesn't care about the details of the event arguments.

你是否在问为什么从一开始就从EventArgs派生出来是有用的?我不得不说,使用C#1它没有多大意义,因为委托转换的工作方式 - 但从C#2开始,它更为明智。它允许事件处理程序向事件注册,即使它不关心事件参数的细节。

For example:

void LogEvent(object sender, EventArgs e)
{
    Console.WriteLine("Event sent from " + sender);
}

...

textArea.KeyPress += LogEvent;

This works even though Control.KeyPress is an event of type KeyPressEventHandler. C# and .NET don't mind that the signature of LogEvent doesn't exactly match the signature of KeyPressEventHandler - it's compatible enough.

即使Control.KeyPress是KeyPressEventHandler类型的事件,这仍然有效。 C#和.NET并不介意LogEvent的签名与KeyPressEventHandler的签名不完全匹配 - 它足够兼容。

Admittedly this would still be feasible if we didn't have EventArgs at all (you could just use object) but given the EventArgs class and the pattern, it makes sense to derive your own event arguments from EventArgs.

不可否认,如果我们根本没有EventArgs(你可以只使用对象),这仍然是可行的,但是给定EventArgs类和模式,从EventArgs派生自己的事件参数是有意义的。

#2

Here is a example of how you might use your code:

以下是如何使用代码的示例:

public class MyClass () {        
    public event EventHandler<ClickedEventArgs> ClickedEvent = delegate {};  //Register the event

    protected void SomethingWasClicked(int x, int y) {    
        ClickedEvent(this, new ClickedEventArgs(x,y));   //Invoke the event that is subscribed to
    }

}

public class AnotherClass () {

    public AnotherClass () {
        MyClass mClass = new MyClass();
        mClass.ClickedEvent += new EventHandler(mClass_clickedEvent);
    }

    protected void mClass_clickedEvent(object sender, ClickedEventArgs e) {
        //Retrieve the X parameter that was passed from the MyClass instance
        int x = e.X;  
    }
}

#3

What is really important here is that you can easily UPGRADE your event later to have MORE details and don't break existing decoupled listeners.

这里真正重要的是,您可以在以后轻松升级您的事件以获得更多详细信息,并且不会破坏现有的解耦侦听器。

#1