Bulk download from Azure Blob Storage with C#

To bulk download files from Azure Blob Storage using C#, you can use the Azure.Storage.Blobs SDK. Below is a step-by-step guide:

1. Install the required NuGet package

Install Azure.Storage.Blobs using NuGet Package Manager:

Install-Package Azure.Storage.Blobs

2. Set up connection details

• Azure Storage Account connection string
• Blob container name
• Local folder path for saving the downloaded files

3. List and Download Blobs in Bulk

• Use BlobContainerClient to get the list of blobs.
• Download each blob asynchronously using DownloadToAsync

  using System;
  using System.IO;
  using System.Threading.Tasks;
  using Azure.Storage.Blobs;
  using Azure.Storage.Blobs.Models;
  
  class Program
  {
      private const string connectionString = "Your_Azure_Storage_Connection_String";
      private const string containerName = "your-container-name";
      private const string downloadFolderPath = @"C:\DownloadedBlobs"; // Local save path
  
      static async Task Main()
      {
          await BulkDownloadBlobsAsync();
      }
  
      private static async Task BulkDownloadBlobsAsync()
      {
          try
          {
              BlobContainerClient containerClient = new BlobContainerClient(connectionString, containerName);
  
              await foreach (BlobItem blobItem in containerClient.GetBlobsAsync())
              {
                  string blobName = blobItem.Name;
                  string localFilePath = Path.Combine(downloadFolderPath, blobName);
  
                  // Create directories if they don't exist
                  Directory.CreateDirectory(Path.GetDirectoryName(localFilePath));
  
                  Console.WriteLine($"Downloading: {blobName}");
  
                  BlobClient blobClient = containerClient.GetBlobClient(blobName);
                  await blobClient.DownloadToAsync(localFilePath);
              }
  
              Console.WriteLine("Bulk download completed.");
          }
          catch (Exception ex)
          {
              Console.WriteLine($"Error: {ex.Message}");
          }
      }
  }

Explanation

• Initialize BlobContainerClient using the storage account connection string.
• List all blobs in the container using GetBlobsAsync().
• Iterate over the blobs and download each file asynchronously.
• Ensure directory structure exists before saving files locally.
• Handle exceptions gracefully.

Optimizing for Large Blob Containers

If your container has thousands of blobs, consider:

• Parallel downloads using Task.WhenAll().
• Filtering blobs by prefix (e.g., download only specific folders).
• Resuming downloads by checking if the file already exists.