WebClient AsyncCompletedEventHandler方法如何附近个参数

WebClient AsyncCompletedEventHandler方法怎么附近个参数？
HttpClient httpClient = new HttpClient(new CookieContainer());//WebClient的重写
  httpClient.DownloadFileCompleted += new System.ComponentModel.AsyncCompletedEventHandler(AsyncDownloadFileCompleted);
//AsyncDownloadFileCompleted方法，我想在这个方法里头再传递一个参数，该如何实现？

 void AsyncDownloadFileCompleted(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
  {

  }

[解决办法]
我也不知道啊 自己看着办吧。