Azure Storage Data Movement Common client library for .NET - version 12.0.0-beta.4

Server Version: 2021-02-12, 2020-12-06, 2020-10-02, 2020-08-04, 2020-06-12, 2020-04-08, 2020-02-10, 2019-12-12, 2019-07-07, and 2020-02-02

Project Status: Beta

This product is in beta. Some features will be missing or have significant bugs. Please see Known Issues for detailed information.

Azure Storage is a Microsoft-managed service providing cloud storage that is highly available, secure, durable, scalable, and redundant.

The Azure Storage Data Movement library is optimized for uploading, downloading and copying customer data.

Currently this version of the Data Movement library only supports Blobs.

Source code | API reference documentation | REST API documentation | Product documentation

Getting started

Install the package

Install the Azure Storage client library for .NET you'd like to use with NuGet and the Azure.Storage.DataMovement client library will be included:

dotnet add package Azure.Storage.DataMovement --prerelease


You need an Azure subscription and a Storage Account to use this package.

To create a new Storage Account, you can use the Azure Portal, Azure PowerShell, or the Azure CLI. Here's an example using the Azure CLI:

az storage account create --name MyStorageAccount --resource-group MyResourceGroup --location westus --sku Standard_LRS

Authenticate the client

Authentication is specific to the targeted storage service. Please see documentation for the individual services

Key concepts

The Azure Storage Common client library contains shared infrastructure like authentication credentials and RequestFailedException.

Thread safety

We guarantee that all client instance methods are thread-safe and independent of each other (guideline). This ensures that the recommendation of reusing client instances is always safe, even across threads.

Additional concepts

Client options | Accessing the response | Long-running operations | Handling failures | Diagnostics | Mocking | Client lifetime


This section demonstrates usage of Data Movement regardless of extension package. Package-specific information and usage samples can be found in that package's documentation. These examples will use local disk and Azure Blob Storage when specific resources are needed for demonstration purposes, but the topics here will apply to other packages.

Setup the TransferManager

Singleton usage of TransferManager is recommended. Providing TransferManagerOptions is optional.

TransferManager transferManager = new TransferManager(new TransferManagerOptions());

Starting New Transfers

Transfers are defined by a source and destination StorageResource. There are two kinds of StorageResource: StorageResourceSingle and StorageResourceContainer. Source and destination of a given transfer must be of the same kind.

StorageResource instances are obtained from StorageResourceProvider instances. See Initializing Local File StorageResource for more information on the resource provider for local files and directories. See the documentation for other DataMovement extension packages for more info on their StorageResourceProvider types.

The below sample demonstrates StorageResourceProvider use to start transfers by uploading a file to Azure Blob Storage, using the Azure.Storage.DataMovement.Blobs package. It uses an Azure.Core token credential with permission to write to the blob.

LocalFilesStorageResourceProvider files = new();
BlobsStorageResourceProvider blobs = new(tokenCredential);
DataTransfer dataTransfer = await transferManager.StartTransferAsync(
    cancellationToken: cancellationToken);
await dataTransfer.WaitForCompletionAsync(cancellationToken);

Resuming Existing Transfers

By persisting transfer progress to disk, DataMovement allows resuming of transfers that failed partway through, or were otherwise paused. To resume a transfer, the transfer manager needs to be setup in the first place with StorageResourceProvider instances (the same ones used above in Starting New Transfers) which are capable of reassembling the transfer components from persisted data.

The below sample initializes the TransferManager such that it's capable of resuming transfers between the local filesystem and Azure Blob Storage, using the Azure.Storage.DataMovement.Blobs package.

Important: Credentials to storage providers are not persisted. Storage access which requires credentials will need its appropriate StorageResourceProvider to be configured with those credentials. Below uses an Azure.Core token credential with permission to the appropriate resources.

LocalFilesStorageResourceProvider files = new();
BlobsStorageResourceProvider blobs = new(tokenCredential);
TransferManager transferManager = new(new TransferManagerOptions()
    ResumeProviders = new List<StorageResourceProvider>() { files, blobs },

To resume a transfer, provide the transfer's ID, as shown below. In the case where your application does not have the desired transfer ID available, use TransferManager.GetTransfersAsync() to find that transfer and it's ID.

DataTransfer resumedTransfer = await transferManager.ResumeTransferAsync(transferId);

Note: the location of persisted transfer data will be different than the default location if TransferCheckpointStoreOptions were set in TransferManagerOptions. To resume transfers recorded in a non-default location, the transfer manager resuming the transfer will also need the appropriate checkpoint store options.

Monitoring Transfers

Transfers can be observed through several mechanisms, depending on your needs.

With DataTransfer

Simple observation can be done through a DataTransfer instance representing an individual transfer. This is obtained on transfer start. You can also enumerate through all transfers on a TransferManager.

A function that writes the status of each transfer to console:

async Task CheckTransfersAsync(TransferManager transferManager)
    await foreach (DataTransfer transfer in transferManager.GetTransfersAsync())
        using StreamWriter logStream = File.AppendText(logFile);
        logStream.WriteLine(Enum.GetName(typeof(StorageTransferStatus), transfer.TransferStatus));

DataTransfer contains property TransferStatus. You can read this to determine the state of the transfer. States include queued for transfer, in progress, paused, completed, and more.

DataTransfer also exposes a task for transfer completion, shown in Starting New Transfers.

With Events via TransferOptions

When starting a transfer, TransferOptions contains multiple events that can be listened to for observation. Below demonstrates listening to the event for individual file completion and logging the result.

A function that listens to status events for a given transfer:

async Task<DataTransfer> ListenToTransfersAsync(TransferManager transferManager,
    StorageResource source, StorageResource destination)
    TransferOptions transferOptions = new();
    transferOptions.SingleTransferCompleted += (SingleTransferCompletedEventArgs args) =>
        using StreamWriter logStream = File.AppendText(logFile);
        logStream.WriteLine($"File Completed Transfer: {args.SourceResource.Path}");
        return Task.CompletedTask;
    return await transferManager.StartTransferAsync(

With IProgress via TransferOptions

When starting a transfer, TransferOptions allows setting a progress handler that contains the progress information for the overall transfer. Granular progress updates will be communicated to the provided IProgress instance.

A function that listens to progress updates for a given transfer with a supplied IProgress<TStorageTransferProgress>:

async Task<DataTransfer> ListenToProgressAsync(TransferManager transferManager, IProgress<StorageTransferProgress> progress,
    StorageResource source, StorageResource destination)
    TransferOptions transferOptions = new()
        ProgressHandler = progress,
        // optionally include the below if progress updates on bytes transferred are desired
        ProgressHandlerOptions = new()
            TrackBytesTransferred = true
    return await transferManager.StartTransferAsync(

Pausing transfers

Transfers can be paused either by a given DataTransfer or through the TransferManager handling the transfer by referencing the transfer ID. The ID can be found on the DataTransfer object you received upon transfer start.

await dataTransfer.PauseIfRunningAsync(cancellationToken);
await transferManager.PauseTransferIfRunningAsync(transferId, cancellationToken);

Handling Failed Transfers

Transfer failure can be observed by checking the DataTransfer status upon completion, or by listening to failure events on the transfer. While checking the DataTransfer may be sufficient for handling single-file transfer failures, event listening is recommended for container transfers.

Below logs failure for a single transfer by checking its status after completion.

await dataTransfer.WaitForCompletionAsync();
if (dataTransfer.TransferStatus == StorageTransferStatus.CompletedWithFailedTransfers)
    using (StreamWriter logStream = File.AppendText(logFile))
        logStream.WriteLine($"Failure for TransferId: {dataTransfer.Id}");

Below logs individual failures in a container transfer via TransferOptions events.

transferOptions.TransferFailed += (TransferFailedEventArgs args) =>
    using (StreamWriter logStream = File.AppendText(logFile))
        // Specifying specific resources that failed, since its a directory transfer
        // maybe only one file failed out of many
        logStream.WriteLine($"Exception occured with TransferId: {args.TransferId}," +
            $"Source Resource: {args.SourceResource.Path}, +" +
            $"Destination Resource: {args.DestinationResource.Path}," +
            $"Exception Message: {args.Exception.Message}");
    return Task.CompletedTask;

Initializing Local File StorageResource

Local filesystem resources are provided by LocalFilesStorageResourceProvider. This provider requires no setup to produce storage resources.

LocalFilesStorageResourceProvider files = new();
StorageResource fileResource = files.FromFile("C:/path/to/file.txt");
StorageResource directoryResource = files.FromDirectory("C:/path/to/dir");



Next steps

Get started with our Blob DataMovement samples.


See the Storage for details on building, testing, and contributing to these libraries.

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