Microsoft deprecated the WindowsAzure.Storage library in favor of Azure.Storage.* libraries, which offers a modernized API with better performance, security, and maintainability. However, migrating from the older package to the newer ones can present challenges due to significant API differences and breaking changes.

This article explores these challenges and provides a step-by-step approach to migrating blob storage operations.

Key Differences Between Packages

Deprecated package

<PackageReference Include="WindowsAzure.Storage" Version="9.3.3" />

New package

<PackageReference Include="Azure.Storage.Blobs" Version="12.24.0" />

The new SDK introduces a more efficient design based on modern .NET principles. Some of the major differences include:

• No direct equivalent for CloudBlockBlob, CloudPageBlob, or CloudBlobDirectory
• Different approach to listing blobs (hierarchical listing vs. flat listing)
• New async paging methods for blob enumeration
• Updated authentication mechanisms

Migration Example: Listing Blobs in a Container

Below, I am comparing the old implementation with the new one.

Old Implementation (WindowsAzure.Storage)

using Microsoft.WindowsAzure.Storage;
using Microsoft.WindowsAzure.Storage.Blob;

/// <summary>
/// Lists blobs in containers
/// </summary>
/// <returns></returns>
public async Task<string> ListContainerBlobs()
{
    StringBuilder builder = new StringBuilder();
    BlobContinuationToken token = null;
    do
    {
        BlobResultSegment resultSegment = await _unmoderatedContainer.ListBlobsSegmentedAsync(token);
        token = resultSegment.ContinuationToken;

        foreach (IListBlobItem item in resultSegment.Results)
        {
            if (item.GetType() == typeof(CloudBlockBlob))
            {
                CloudBlockBlob blob = (CloudBlockBlob)item;
                builder.AppendLine($"Block blob of length {blob.Properties.Length}: {blob.Uri}");
            }

            else if (item.GetType() == typeof(CloudPageBlob))
            {
                CloudPageBlob pageBlob = (CloudPageBlob)item;

                builder.AppendLine($"Page blob of length {pageBlob.Properties.Length}: {pageBlob.Uri}");
            }

            else if (item.GetType() == typeof(CloudBlobDirectory))
            {
                CloudBlobDirectory directory = (CloudBlobDirectory)item;

                builder.AppendLine($"Directory: {directory.Uri}");
            }
        }
    } while (token != null);

    return builder.ToString();
}

New Implementation (Azure.Storage.Blobs)

using Azure.Storage.Blobs;

/// <summary>
/// Lists blobs in containers
/// </summary>
/// <returns></returns>
public async Task<string> ListContainerBlobs()
{
    StringBuilder builder = new StringBuilder();
    string containerUri = _unmoderatedContainer.Uri.ToString();
    string continuationToken = null;

    do
    {
        var resultSegment = _unmoderatedContainer.GetBlobsByHierarchyAsync(delimiter: "/").AsPages(continuationToken);
        await foreach (var blobPage in resultSegment)
        {
            continuationToken = blobPage.ContinuationToken;

            foreach (var item in blobPage.Values)
            {
                if (item.IsBlob)
                {
                    var blobItem = item.Blob;
                    var blobUri = $"{containerUri}/{blobItem.Name}";
                    builder.AppendLine($"Block blob of length {blobItem.Properties.ContentLength}: {blobUri}");
                }
                else if (item.IsPrefix)
                {
                    var prefixItem = item.Prefix;
                    builder.AppendLine($"Directory: {containerUri}/{prefixItem}");
                }
            }
        }
    } while (continuationToken != null);

    return builder.ToString();
}

Challenges and How to Overcome Them

1. CloudBlockBlob and CloudPageBlob Are No Longer Available

• In the new SDK, BlobItem represents blobs, and BlobProperties stores metadata.
• The IsBlob property helps differentiate between blobs and directories.

2. No CloudBlobDirectory Equivalent

• Instead of CloudBlobDirectory, the new SDK uses Prefix to represent virtual directories.

3. Continuation Tokens Work Differently

• In WindowsAzure.Storage, pagination uses BlobContinuationToken.
• In Azure.Storage.Blobs, pagination is done via AsPages() with a continuation token string.

4. Different Methods for Listing Blobs

• ListBlobsSegmentedAsync() is replaced by GetBlobsByHierarchyAsync().AsPages().
• The new approach allows for hierarchical navigation using delimiters.

Conclusion

Migrating from WindowsAzure.Storage to Azure.Storage.Blobs requires adapting to a more modern, efficient API. The transition is not always straightforward, as there are significant differences in class structures, methods, and pagination mechanisms. A direct conversion is not possible in many cases, requiring us to rethink the implementation.

While these changes can be challenging, they ultimately lead to better performance, improved security, and more maintainable code. Try understanding these differences and planning the migration carefully.