WebClient 超时 Windows Phone 8

Question

我想在等待 Web 请求期间运行任务。如果任务在请求可以返回响应之前完成，那么我会显示一条消息“服务器花费的时间太长”。我正在使用WebClient 对象，如何管理超时？

public Class Result
{
   protected override void OnNavigatedTo(NavigationEventArgs e)
   {
      if (NavigationContext.QueryString.TryGetValue("critere", out sCritere))
      {
         try
         {
            _datamanager = new DataManager();
            _datamanager.m_evt_Client_DownloadStringCompleted += OnDownloadStringCompleted;
            _datamanager.DownloadXmlData(DataManager.URL_RECHERCHE, sCritere);

            //HERE I NEED TO RUN A TIMER If the response is too long i would display a message                          

          }
          catch(Exception ex)
          {
             MessageBox.Show(ex.Message, "Erreur", MessageBoxButton.OK);
             NavigationService.GoBack();
             NavigationService.RemoveBackEntry();
          }
       }
    }
  }

public Class DataManager
{
   public void DownloadXmlData(string uri, string critere = "")
   {
      try
      {   
         WebClient client = new WebClient();
         client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);
         client.Credentials = new NetworkCredential(UserSaved, PasswordSaved, domain);
         client.DownloadStringAsync(new Uri(uri + critere));
       }
       catch(WebException )
       {
          throw new WebException(MyExceptionsMessages.Webexception) ;
       }
       catch (Exception )
       {
          throw new UnknowException(MyExceptionsMessages.UnknownError);
       }
    }

   public void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
   {
      //raise Downloadstringcompleted event if error==null
   }
}

Answer 1

你可以使用 BackgroundWorker..

BackgroundWorker bw = new BackgroundWorker();
bw.DoWork += (s, e) =>
{
    // your task to do while webclient is downloading
};
bw.RunWorkerCompleted += (s, e) =>
{
    // check whether DownloadStringCompleted is fired or not
    // if not, cancel the WebClient's asynchronous call and show your message.
    client.CancelAsync();
    MessageBox.Show("message");
}

client.DownloadStringAsync(uri);
bw.RunWorkerAsync();