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.

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