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

2 Comments

Join the conversation! Your thoughts help the community grow.

Ger F Versteeg9y ago
Hello Tahir, nice source but I dont understand "settings" in : //Account CloudStorageAccount storageAccount = new CloudStorageAccount( new StorageCredentials(settings.StorageAccount, settings.StorageKey), false); Please can you help me with a explanation? Best Regards Ger F.
- Guest User9y ago
  Thanks Ger. "settings" is just a POCO that holds the settings passed (from interface) to the class that interacts with Blog storage.