c# - CA1009 : Declare event handlers correctly?

Question

我有以下事件，我类的消费者可以连接以获取内部诊断消息。

public event EventHandler<string> OutputRaised;

我用这个函数引发事件

protected virtual void OnWriteText(string e)
    {
        var handle = this.OutputRaised;
        if (handle != null)
        {
            var message = string.Format("({0}) : {1}", this.Port, e);
            handle(this, message);
        }
    }

为什么我能正确获取 CA1009 声明事件处理程序？我找到的所有答案似乎并不真正适用于我的场景...只是想了解一下，我还没有真正扎实地掌握事件和委托(delegate)。

CA1009 引用:http://msdn.microsoft.com/en-us/library/ms182133.aspx

Answer 1

根据'规则'，EventHandler的类型参数应该继承自EventArgs:

Event handler methods take two parameters. The first is of type System.Object and is named 'sender'. This is the object that raised the event. The second parameter is of type System.EventArgs and is named 'e'. This is the data that is associated with the event. For example, if the event is raised whenever a file is opened, the event data typically contains the name of the file.

在您的情况下，可能是这样的:

public class StringEventArgs : EventArgs
{
   public string Message {get;private set;}

   public StringEventArgs (string message)
   {
      this.Message = message;
   }

}

和你的事件处理器:

public event EventHandler<StringEventArgs> OutputRaised;

引发事件时，当然应该创建 StringEventArgs 类的实例:

protected virtual void OnWriteText( string message )
{
    var handle = this.OutputRaised;
    if (handle != null)
    {
        var message = string.Format("({0}) : {1}", this.Port, e);
        handle(this, new StringEventArgs(message));
    }
}

我还想补充一点，从理论上讲，您的代码没有任何问题。编译器不会报错，您的代码会正常工作。 EventHandler<T>委托(delegate)没有指定类型参数应该继承自EventArgs . FxCop 表示您违反了声明事件的“设计规则”。