如何解决 BackgroundUploadAsync 错误？

Question

我正在使用 BackgroundUploadAsync API 将文件上传到 OneDrive。大多数时候该函数工作正常，但有时调用 returns 并出现此错误消息：

System is busy with a previous background Upload...

我尝试关闭并重新启动应用程序，但我仍然遇到同样的错误。

知道为什么会这样吗？如何重新初始化与 OneDrive 的连接？

这是执行上传的代码：

public static async Task<string> BackgroundUploadFile<T>(
    string skydriveFolderId,
    T objectToSerialize,
    string fileNameInSkyDrive,
    BackgroundTransferPreferences backgroundTransferPreferences =
        BackgroundTransferPreferences.AllowCellularAndBattery)
{
    string fileId = string.Empty;
    try
    {
        var storageFolder = await GetSharedTransfersFolder();

        StorageFile isolatedstorageFile = await storageFolder.CreateFileAsync(
            fileNameInSkyDrive,
            CreationCollisionOption.ReplaceExisting);
        using (var writer = new StreamWriter
            (await isolatedstorageFile.OpenStreamForWriteAsync()))
        {
            // convert to string
            var _String = Serialize(objectToSerialize);
            await writer.WriteAsync(_String);
        }

        Client.BackgroundTransferPreferences = backgroundTransferPreferences;
        LiveOperationResult liveOpResult = await Client.BackgroundUploadAsync(
            skydriveFolderId,
            new Uri("/shared/transfers/" + fileNameInSkyDrive, UriKind.Relative),
            OverwriteOption.Overwrite);
        fileId = (string)liveOpResult.Result["id"];
        Debug.WriteLine("BackgroundUploadFile: " + fileNameInSkyDrive);
    }
    catch (Exception e)
    {
        MessageBox.Show(e.Message, "Upload Error", MessageBoxButton.OK);

        Debug.WriteLine("\nError - BackgroundUploadFile: " + e.Message);
    }

    return fileId;
}

此外，我 "suspicion" OneDrive 正在锁定帐户，因为有后台任务 "stuck" 而 OneDrive 没有 release/free 它们？！

Answer 1

你有机会在其他任何地方打电话给 BackgroundUploadAsync 吗？尝试用 SemaphoreSlim 任何地方 保护它，你可能会使用它：

// class member
SemaphoreSlim  _semaphore = new SemaphoreSlim(1); 

public static async Task<string> BackgroundUploadFile<T>(..)
{
    // ...

    LiveOperationResult liveOpResult;
    await _semaphore.WaitAsync();
    try
    {
        liveOpResult = await Client.BackgroundUploadAsync(
            skydriveFolderId,
            new Uri("/shared/transfers/" + fileNameInSkyDrive, UriKind.Relative),
            OverwriteOption.Overwrite);
    }
    finally
    {
        _semaphore.Release();
    }

    // ...
}

Answer 2

我无法让 BackgroundUploadFile 按预期工作，而是使用附加的上传功能解决了这个问题：

        public static async Task<string> UploadFile<T>( string skydriveFolderId,
                                                    T objectToSerialize,
                                                    string fileNameInSkyDrive )
        {
        string fileID = string.Empty;
        using ( var memoryStream = new MemoryStream() )
            {
            try
                {
                var serializer = new DataContractJsonSerializer( objectToSerialize.GetType() );
                serializer.WriteObject( memoryStream, objectToSerialize );

                memoryStream.Seek( 0, SeekOrigin.Begin );

                LiveOperationResult liveOpResult = await Client.UploadAsync( skydriveFolderId, fileNameInSkyDrive, memoryStream, OverwriteOption.Overwrite );
                fileID = (string)liveOpResult.Result [ "id" ];
                Debug.WriteLine( "\nUploadFile: " + fileNameInSkyDrive );
                }
            catch ( Exception e )
                {
                MessageBox.Show( e.Message, "Upload Error", MessageBoxButton.OK );

                Debug.WriteLine( "\nError - UploadFile: " + e.Message );
                }
            }

        return fileID;
        }

感谢

如何解决 BackgroundUploadAsync 错误？

How to solve BackgroundUploadAsync error?

c#

windows-phone

async-await

windows-phone-8

live-sdk