UploadOperation UploadOperation UploadOperation UploadOperation Class

Performs an asynchronous upload operation. For an overview of Background Transfer capabilities, see Transferring data in the background. Download the Background Transfer sample for examples in JavaScript, C#, and C++.

Syntax

Declaration

public sealed class UploadOperationpublic sealed class UploadOperationPublic NotInheritable Class UploadOperationpublic sealed class UploadOperation

Remarks

After app termination, an app should enumerate all existing UploadOperation instances at next start-up using GetCurrentUploadsAsync(). When a Windows Store app using Background Transfer is terminated, incomplete uploads will persist in the background. If the app is restarted after termination and these incomplete operations are not enumerated and re-introduced to the current session, they will go stale and continue to occupy device resources.Timeout considerations

  • 1.) When establishing a new connection for an upload over TCP/SSL, the connection attempt is aborted if not established within five minutes.
  • 2.) After the connection has been established, an HTTP request message that has not received a response within two minutes is aborted. Assuming there is Internet connectivity, Background Transfer will retry an upload up to three times. In the event Internet connectivity is not detected, additional attempts will not be made until it is.

Debugging Guidance

Stopping a debugging session in Microsoft Visual Studio is comparable to closing your app; PUT uploads are paused and POST uploads are aborted. Even while debugging, your app should enumerate and then pause, restart, or cancel any persisted uploads.

However, if Microsoft Visual Studio project updates, like changes to the app manifest, require that the app is uninstalled and re-deployed for debugging, GetCurrentUploadsAsync() cannot enumerate persisted operations created using the previous app deployment.

Examples

The following example demonstrates how to configure and begin a basic upload operation, and is based on the Background Transfer sample offered in the Windows Sample Gallery.

        var upload = null;
        var promise = null;

        function UploadFile (uriString, file) {
            try {

                var uri = Windows.Foundation.Uri(uriString);
                var uploader = new Windows.Networking.BackgroundTransfer.BackgroundUploader();

                // Set a header, so the server can save the file (this is specific to the sample server).
                uploader.setRequestHeader("Filename", file.name);

                // Create a new upload operation.
                upload = uploader.createUpload(uri, file);

                // Start the upload and persist the promise to be able to cancel the upload.
                promise = upload.startAsync().then(complete, error, progress);
            } catch (err) {
                displayError(err);
            }
        };

        using Windows.Foundation; 
        using Windows.Networking.BackgroundTransfer;
        using Windows.Storage.Pickers;
        using Windows.Storage;

        private async void StartUpload_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                Uri uri = new Uri(serverAddressField.Text.Trim());
                FileOpenPicker picker = new FileOpenPicker();
                picker.FileTypeFilter.Add("*");
                StorageFile file = await picker.PickSingleFileAsync();

                BackgroundUploader uploader = new BackgroundUploader();
                uploader.SetRequestHeader("Filename", file.Name);

                UploadOperation upload = uploader.CreateUpload(uri, file);

                // Attach progress and completion handlers.
                HandleUploadAsync(upload, true);
            }
            catch (Exception ex)
            {
                LogException("Upload Error", ex);
            }
        }

Properties summary

Gets and sets the cost policy for the upload.

Note

Group may be altered or unavailable for releases after Windows 8.1. Instead, use TransferGroup.

Gets a string value indicating the group the upload belongs to.

This is a unique identifier for a specific upload operation. A GUID associated to a upload operation will not change for the duration of the upload.

Gets the method to use for the upload.

Gets or sets the transfer priority of this upload operation when within a BackgroundTransferGroup. Possible values are defined by BackgroundTransferPriority.

Gets the current progress of the upload operation.

Gets the URI to upload from.

Specifies the IStorageFile to upload.

Gets the group that this upload operation belongs to.

Methods summary

Returns an asynchronous operation that can be used to monitor progress and completion of the attached upload. Calling this method allows an app to attach upload operations that were started in a previous app instance.

Gets the response information.

Gets the partially uploaded response at the specified location.

Starts an asynchronous upload operation.

Properties

  • CostPolicy
    CostPolicy
    CostPolicy
    CostPolicy

    Gets and sets the cost policy for the upload.

    public BackgroundTransferCostPolicy CostPolicy { get; set; }public BackgroundTransferCostPolicy CostPolicy { get; set; }Public ReadWrite Property CostPolicy As BackgroundTransferCostPolicypublic BackgroundTransferCostPolicy CostPolicy { get; set; }

    Property Value

  • Group
    Group
    Group
    Group
    Note

    Group may be altered or unavailable for releases after Windows 8.1. Instead, use TransferGroup.

    Gets a string value indicating the group the upload belongs to.

    public string Group { get; }public string Group { get; }Public ReadOnly Property Group As stringpublic string Group { get; }

    Property Value

    • string
      string
      string
      string

      The group name.

  • Guid
    Guid
    Guid
    Guid

    This is a unique identifier for a specific upload operation. A GUID associated to a upload operation will not change for the duration of the upload.

    public Guid Guid { get; }public Guid Guid { get; }Public ReadOnly Property Guid As Guidpublic Guid Guid { get; }

    Property Value

    • System.Guid
      System.Guid
      System.Guid
      System.Guid

      The unique ID for this upload operation.

  • Method
    Method
    Method
    Method

    Gets the method to use for the upload.

    public string Method { get; }public string Method { get; }Public ReadOnly Property Method As stringpublic string Method { get; }

    Property Value

    • string
      string
      string
      string

      The method to use for the upload. This value can be GET, PUT, POST, RETR, STOR, or any custom value supported by the server.

  • Priority
    Priority
    Priority
    Priority

    Gets or sets the transfer priority of this upload operation when within a BackgroundTransferGroup. Possible values are defined by BackgroundTransferPriority.

    public BackgroundTransferPriority Priority { get; set; }public BackgroundTransferPriority Priority { get; set; }Public ReadWrite Property Priority As BackgroundTransferPrioritypublic BackgroundTransferPriority Priority { get; set; }

    Property Value

  • Progress
    Progress
    Progress
    Progress

    Gets the current progress of the upload operation.

    public BackgroundUploadProgress Progress { get; }public BackgroundUploadProgress Progress { get; }Public ReadOnly Property Progress As BackgroundUploadProgresspublic BackgroundUploadProgress Progress { get; }

    Property Value

    Remarks

    The value of the Progress property is updated in real time, which means that the value can change while a progress handler is executing. As a best practice, create a local copy of the Progress property at the beginning of your progress handler, and use only that copy in your progress handler, to maintain a consistent view of progress as your handler executes.

  • RequestedUri
    RequestedUri
    RequestedUri
    RequestedUri

    Gets the URI to upload from.

    public Uri RequestedUri { get; }public Uri RequestedUri { get; }Public ReadOnly Property RequestedUri As Uripublic Uri RequestedUri { get; }

    Property Value

  • SourceFile
    SourceFile
    SourceFile
    SourceFile

    Specifies the IStorageFile to upload.

    public IStorageFile SourceFile { get; }public IStorageFile SourceFile { get; }Public ReadOnly Property SourceFile As IStorageFilepublic IStorageFile SourceFile { get; }

    Property Value

  • TransferGroup
    TransferGroup
    TransferGroup
    TransferGroup

    Gets the group that this upload operation belongs to.

    public BackgroundTransferGroup TransferGroup { get; }public BackgroundTransferGroup TransferGroup { get; }Public ReadOnly Property TransferGroup As BackgroundTransferGrouppublic BackgroundTransferGroup TransferGroup { get; }

    Property Value

Methods

  • AttachAsync()
    AttachAsync()
    AttachAsync()
    AttachAsync()

    Returns an asynchronous operation that can be used to monitor progress and completion of the attached upload. Calling this method allows an app to attach upload operations that were started in a previous app instance.

    public IAsyncOperationWithProgress<UploadOperation, UploadOperation> AttachAsync()public IAsyncOperationWithProgress<UploadOperation, UploadOperation> AttachAsync()Public Function AttachAsync() As IAsyncOperationWithProgress( Of UploadOperation, UploadOperation )public IAsyncOperationWithProgress<UploadOperation, UploadOperation> AttachAsync()

    Returns

    • Upload operation with callback.

    Remarks

    While this method can be called from multiple app instances, developers should not attach callbacks from the primary app instance in a background task. This will cause BackgroundTransferHost.exe to hang.

    Examples

            function AttachUpload (loadedUpload) {
                try {
                    upload = loadedUpload;
                    promise = upload.attachAsync().then(complete, error, progress);
                } catch (err) {
                    displayError(err);
                }
            };
    
  • GetResponseInformation()
    GetResponseInformation()
    GetResponseInformation()
    GetResponseInformation()

    Gets the response information.

    public ResponseInformation GetResponseInformation()public ResponseInformation GetResponseInformation()Public Function GetResponseInformation() As ResponseInformationpublic ResponseInformation GetResponseInformation()

    Returns

    Remarks

    This method returns an object that contains information about the current server response. When calling this method multiple times, the object returned will be the same as long as there is no new server response information available. Sometimes however, one upload consists of multiple requests to a server. If a request gets aborted due to some non-fatal error (e.g. machine lost internet connectivity, cost policy required upload to pause, application called Pause(), etc.), Background Transfer will invoke a new request and try to restart the upload. The response information from the server for this second request may be different than the one returned by the first request.

    Returns null if any of the following conditions is true.

    • The transfer associated with the UploadOperation is being made using a protocol other than HTTP (e.g., FTP).
    • The UploadOperation hasn't yet begun.
    • There was a failure before any response from the server was received (e.g., connection couldn't be established).
  • GetResultStreamAt(UInt64)
    GetResultStreamAt(UInt64)
    GetResultStreamAt(UInt64)
    GetResultStreamAt(UInt64)

    Gets the partially uploaded response at the specified location.

    public IInputStream GetResultStreamAt(UInt64 position)public IInputStream GetResultStreamAt(UInt64 position)Public Function GetResultStreamAt(position As UInt64) As IInputStreampublic IInputStream GetResultStreamAt(UInt64 position)

    Parameters

    • position
      System.UInt64
      System.UInt64
      System.UInt64
      System.UInt64

      The position at which to start reading.

    Returns

  • StartAsync()
    StartAsync()
    StartAsync()
    StartAsync()

    Starts an asynchronous upload operation.

    public IAsyncOperationWithProgress<UploadOperation, UploadOperation> StartAsync()public IAsyncOperationWithProgress<UploadOperation, UploadOperation> StartAsync()Public Function StartAsync() As IAsyncOperationWithProgress( Of UploadOperation, UploadOperation )public IAsyncOperationWithProgress<UploadOperation, UploadOperation> StartAsync()

    Returns

    • An asynchronous upload operation that includes progress updates.

    Remarks

    An upload operation must be scheduled using one of the CreateUpload(Uri, IStorageFile), CreateUploadAsync(Uri, IIterable<BackgroundTransferContentPart>) , or CreateUploadFromStreamAsync(Uri, IInputStream) methods before the StartAsync() method is called.

    Important

    Queuing up a large number of transfers on the main UI thread can result in degraded performance of your app's UI, even though the call is awaitable. If you are queuing up a large number of transfers, it is recommended that you call StartAsync on a background worker thread as in the following example.

    operation = await Task.Run(() => { return myUploadOperation.StartAsync(); });
    

Device family

Windows 10 (introduced v10.0.10240.0)

API contract

Windows.Foundation.UniversalApiContract (introduced v1)

Capabilities

internetClientServer
privateNetworkClientServer
internetClient

Attributes

Windows.Foundation.Metadata.ContractVersionAttribute
Windows.Foundation.Metadata.MarshalingBehaviorAttribute

Details

Assembly

Windows.Networking.BackgroundTransfer.dll