如何去除匿名方法的回調監聽？

Question

我寫了一些類：

public class A 
{ 
    public A() 
    { 
     serviceAdapter.CompletedCallBackEvent += new EventHandler(foo); 
     . 
     . 
     . 
    } 

    void foo(object sender, EventArgs e) 
    { 
     serviceAdapter.CompletedCallBackEvent -= new EventHandler(foo); 
    } 
} 

現在，我要換一些匿名的回調監聽器 - 但我不知道如何刪除回調監聽器的匿名方法。

class A 
{ 
    public A() 
    { 
      serviceAdapter.CompletedCallBackEvent += delegate(object sender, EventArgs ee) 
      { 
        ... need to remove the listener to the event. 
      } 
    } 
} 

Answer 1

您可以簡單地將您的委託/處理程序分配給一個私有變量。

private EventHander _handler = null; 

public A() 
{   
    _handler = delegate(object sender, EventArgs ee) 
     {   
      ServiceAdapter.CompletedCallBackEvent -= _handler; 
     }; 
    ServiceAdapter.CompletedCallBackEvent += _handler; 
} 

Answer 2

您不能刪除這樣的匿名委託。有關匿名代表的信息，請參見MSDN。另外值得一讀this article

您可能能夠做到：

 public A() 
    { 
     EventHandler myHandler = null; 
     myHandler = new EventHandler(delegate(object s, EventArgs e) 
      { 
       serviceAdapter.CompletedCallbackEvent -= myHandler; 
      }); 

     serviceAdapter.CompletedCallBackEvent += myHandler; 
    }