如何在使用BackgroundDownloader并行下载时更新UI？

在WinRT中。我在后台方法下载并下载进度应在UI部分更新。如何在使用BackgroundDownloader并行下载时更新UI？

我的代码是

   public async static Task DownloadSingleFile(string name, SoundClass sc) 
      { 
        var dl = new BackgroundDownloader(); 
        dl.CostPolicy = BackgroundTransferCostPolicy.Always; 
        file = await localSoundsFolder.CreateFileAsync(name, CreationCollisionOption.ReplaceExisting); 

        var d = dl.CreateDownload(new Uri(uriToDownloadFrom), file); 
        d.Priority = BackgroundTransferPriority.Default; 

        var progressCallback = new Progress<DownloadOperation>(DownloadProgress); 
        try 
        { 
         await d.StartAsync().AsTask(cancellationToken.Token, progressCallback); 
         CancellationTokenSource token = Utility.cancellationList[sc]; 
         if (token != null) 
         { 
          token.Cancel(); 
          Utility.cancellationList.Remove(sc); 
          Debug.WriteLine("The sc has been removed from the download list"); 
         } 
        } 
        catch 
        { 
         return; 
        } 
       }

以及下载方法看起来像这样

 private static void DownloadProgress(DownloadOperation download) 
     { 
      Debug.WriteLine("Callback"); 
      var value = download.Progress.BytesReceived * 100/download.Progress.TotalBytesToReceive; 
      Debug.WriteLine("The bytesReceived is {0} and total bytes is {1}", download.Progress.BytesReceived.ToString(), download.Progress.TotalBytesToReceive.ToString()); 
      new System.Threading.ManualResetEvent(false).WaitOne(10); 
      //Update the UI here 
      if (download.Progress.Status == BackgroundTransferStatus.Completed || value >= 100) 
      { 
       //Perform opertaion 
      } 
     }

我现在面临的问题是，因为我有多个下载操作发生的事情，我不能直接执行该操作更新用户界面。我想知道如何发送参数DownloadProgress方法，该方法绑定到UI并帮助更新操作。

来源

2015-10-14 AbsoluteSith

能否请你告诉或共享一些资源，这是多个文件的执行有帮助与实时进度和取消选项下载 –

你可以使用lambda表达式这个：

int downloadId = ...; 
var progressCallback = new Progress<DownloadOperation>(x => DownloadProgress(x, downloadId));

那么你的进步更新可以使用它：

private static void DownloadProgress(DownloadOperation download, int downloadId) 
{ 
    ... // use downloadId 
}

来源

2015-10-14 17:43:36

谢谢！正是我在找什么！ – AbsoluteSith

如何在使用BackgroundDownloader并行下载时更新UI？

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