Azure Blob Storage In ASP.NET Core 2.0

Problem

How to use Azure Blob storage in ASP.NET Core.

Solution

Create a class library and add NuGet package - WindowsAzure.Storage

Add a class to encapsulate settings,

public class AzureBlobSetings
 {
     public AzureBlobSetings(string storageAccount,
                                    string storageKey,
                                    string containerName)
     {
         if (string.IsNullOrEmpty(storageAccount))
             throw new ArgumentNullException("StorageAccount");

         if (string.IsNullOrEmpty(storageKey))
             throw new ArgumentNullException("StorageKey");

         if (string.IsNullOrEmpty(containerName))
             throw new ArgumentNullException("ContainerName");

         this.StorageAccount = storageAccount;
         this.StorageKey = storageKey;
         this.ContainerName = containerName;
     }

     public string StorageAccount { get; }
     public string StorageKey { get; }
     public string ContainerName { get; }
 }

Add a class to encapsulate a blob item,

public class AzureBlobItem
  {
      public AzureBlobItem(IListBlobItem item)
      {
          this.Item = item;
      }

      public IListBlobItem Item { get; }

      public bool IsBlockBlob => Item.GetType() == typeof(CloudBlockBlob);
      public bool IsPageBlob => Item.GetType() == typeof(CloudPageBlob);
      public bool IsDirectory => Item.GetType() == typeof(CloudBlobDirectory);

      public string BlobName => IsBlockBlob ? ((CloudBlockBlob)Item).Name :
                                IsPageBlob ? ((CloudPageBlob)Item).Name :
                                IsDirectory ? ((CloudBlobDirectory)Item).Prefix :
                                "";

      public string Folder => BlobName.Contains("/") ?
                       BlobName.Substring(0, BlobName.LastIndexOf("/")) : "";

      public string Name => BlobName.Contains("/") ?
                       BlobName.Substring(BlobName.LastIndexOf("/") + 1) : BlobName;
  }

Add a class to encapsulate storage access. Add a private helper methods to access storage,

    private async Task<CloudBlobContainer> GetContainerAsync()
        {
            //Account
            CloudStorageAccount storageAccount = new CloudStorageAccount(
         new StorageCredentials(settings.StorageAccount, settings.StorageKey), false);

            //Client
            CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();

            //Container
            CloudBlobContainer blobContainer =
blobClient.GetContainerReference(settings.ContainerName);
            await blobContainer.CreateIfNotExistsAsync();

            return blobContainer;
        }

        private async Task<CloudBlockBlob> GetBlockBlobAsync(string blobName)
        {
            //Container
            CloudBlobContainer blobContainer = await GetContainerAsync();

            //Blob
            CloudBlockBlob blockBlob = blobContainer.GetBlockBlobReference(blobName);

            return blockBlob;
        }

        private async Task<List<AzureBlobItem>> GetBlobListAsync(
bool useFlatListing = true)
        {
            //Container
            CloudBlobContainer blobContainer = await GetContainerAsync();

            //List
            var list = new List<AzureBlobItem>();
            BlobContinuationToken token = null;
            do
            {
                BlobResultSegment resultSegment =
                    await blobContainer.ListBlobsSegmentedAsync("", useFlatListing,
new BlobListingDetails(), null, token, null, null);
                token = resultSegment.ContinuationToken;

                foreach (IListBlobItem item in resultSegment.Results)
                {
                    list.Add(new AzureBlobItem(item));
                }
            } while (token != null);

            return list.OrderBy(i => i.Folder).ThenBy(i => i.Name).ToList();
        }

Now add public methods to upload and download blob items,

public async Task UploadAsync(string blobName, string filePath)
      {
          //Blob
          CloudBlockBlob blockBlob = await GetBlockBlobAsync(blobName);

          //Upload
          using (var fileStream = System.IO.File.Open(filePath, FileMode.Open))
          {
              fileStream.Position = 0;
              await blockBlob.UploadFromStreamAsync(fileStream);
          }
      }

      public async Task UploadAsync(string blobName, Stream stream)
      {
          //Blob
          CloudBlockBlob blockBlob = await GetBlockBlobAsync(blobName);

          //Upload
          stream.Position = 0;
          await blockBlob.UploadFromStreamAsync(stream);
      }

      public async Task<MemoryStream> DownloadAsync(string blobName)
      {
          //Blob
          CloudBlockBlob blockBlob = await GetBlockBlobAsync(blobName);

          //Download
          using (var stream = new MemoryStream())
          {
              await blockBlob.DownloadToStreamAsync(stream);
              return stream;
          }
      }

      public async Task DownloadAsync(string blobName, string path)
      {
          //Blob
          CloudBlockBlob blockBlob = await GetBlockBlobAsync(blobName);

          //Download
          await blockBlob.DownloadToFileAsync(path, FileMode.Create);
      }

Add methods to get a list of blob items,

public async Task<List<AzureBlobItem>> ListAsync()
   {
       return await GetBlobListAsync();
   }

   public async Task<List<string>> ListFoldersAsync()
   {
       var list = await GetBlobListAsync();
       return list.Where(i => !string.IsNullOrEmpty(i.Folder))
                  .Select(i => i.Folder)
                  .Distinct()
                  .OrderBy(i => i)
                  .ToList();
   }

Inject and use storage helper,

public class HomeController : Controller
  {
      private readonly IAzureBlobStorage blobStorage;

      public HomeController(IAzureBlobStorage blobStorage)
      {
          this.blobStorage = blobStorage;
      }

Note

Sample code has a controller with actions for listing, downloading and uploading items.

In ASP.NET Core Web Application, configure services,

public void ConfigureServices(
        IServiceCollection services)
    {
        services.AddScoped<IAzureBlobStorage>(factory =>
        {
            return new AzureBlobStorage(new AzureBlobSetings(
                storageAccount: Configuration["Blob_StorageAccount"],
                storageKey: Configuration["Blob_StorageKey"],
                containerName: Configuration["Blob_ContainerName"]));
        });

        services.AddMvc();
    }

Discussion

The sample code will require you to set up an Azure account, blob storage account, and container. Instructions for these can be found  here.

Source Code

GitHub