在c＃中从Windows azure中删除blob

Question

I have code which inserts a blob into storage, and allows the user to view a list of the blobs, and an individual blob. However, I now can't get the blob to delete, the error that appears is

"An exception of type 'System.ServiceModel.FaultException`1' occurred in System.ServiceModel.ni.dll but was not handled in user code. Additional information: The remote server returned an error: (404) Not Found."

The code in the WCF service is

public void DeleteBlob(string guid, string uri)
{
    //create the storage account with shared access key
    CloudStorageAccount storageAccount = CloudStorageAccount.Parse(accountDetails);

    CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
    CloudBlobContainer container = blobClient.GetContainerReference(guid);

    CloudBlockBlob blob = container.GetBlockBlobReference(uri);
    blob.DeleteIfExists();
}

and then I access this in the mobile client application through SOAP services like:

private void mnuDelete_Click(object sender, EventArgs e)
{
    MessageBoxResult message = MessageBox.Show("Are you sure you want to delete this image?", "Delete", MessageBoxButton.OKCancel);
    if (message == MessageBoxResult.OK)
    {
        Service1Client svc = new Service1Client();
        svc.DeleteBlobCompleted += new EventHandler<AsyncCompletedEventArgs>(svc_DeleteBlobCompleted);
        svc.DeleteBlobAsync(container, uri);
    }
}
void svc_DeleteBlobCompleted(object sender, AsyncCompletedEventArgs e)
{
    if (e.Error == null) {
        NavigationService.Navigate(new Uri("/Pages/albums.xaml", UriKind.Relative));
    }
    else {
        MessageBox.Show("Unable to delete this photo at this time", "Error", MessageBoxButton.OK);
    }
}

I also use SAS token to save the blob in the first place - I don't know whether this makes a difference?

Answer 1

In Azure Storage Client Library 4.0, we changed Get*Reference methods to accept relative addresses only. So, if you are using the latest library and the parameter "uri" is an absolute address, you should change it to either to the blob name or you should use the CloudBlockBlob constructor that takes an Uri and a StorageCredentials object.

Please see all such breaking changes in our GitHub repository .

Answer 2

I am using WindowsAzure.Storage (v8.1.4) in my ASP.NET Core MVC web app (v1.1.3).

I have an image crop and resize feature on my web app so I decide to use Azure Blob Storage to store the raw(user uploaded) pictures and the cropped (after resize) pictures.

One important thing to keep in mind even you're using the CloudBlockBlob constructor with the absolute uri is that you still need to pass your storage account credentials into CloudBlockBlob constructor.

public class AzureBlobStorageService : IBlobStorageService
{
    private readonly AzureBlobConnectionConfigurations _azureBlobConnectionOptions;
    private readonly CloudStorageAccount _storageAccount;
    private readonly CloudBlobClient _blobClient;

    public AzureBlobStorageService(IOptions<AzureBlobConnectionConfigurations> azureBlobConnectionAccessor)
    {
        _azureBlobConnectionOptions = azureBlobConnectionAccessor.Value;

        _storageAccount = CloudStorageAccount.Parse(_azureBlobConnectionOptions.StorageConnectionString);
        _blobClient = _storageAccount.CreateCloudBlobClient();
    }

    public async Task<Uri> UploadAsync(string containerName, string blobName, IFormFile image)
    {
        ...
    }

    public async Task<Uri> UploadAsync(string containerName, string blobName, byte[] imageBytes)
    {
        ...
    }

    public async Task<byte[]> GetBlobByUrlAsync(string url, bool deleteAfterFetch = false)
    {
        // This works
        var blockBlob = new CloudBlockBlob(new Uri(url), _storageAccount.Credentials);

        // Even this will fail
        //var blockBlob = new CloudBlockBlob(new Uri(url));

        await blockBlob.FetchAttributesAsync();

        byte[] arr = new byte[blockBlob.Properties.Length];
        await blockBlob.DownloadToByteArrayAsync(arr, 0);

        if (deleteAfterFetch)
        {
            await blockBlob.DeleteIfExistsAsync();
        }

        return arr;
    }

    private async Task<CloudBlobContainer> CreateContainerIfNotExistAsync(string containerName)
    {
        var container = _blobClient.GetContainerReference(containerName);
        if (!await container.ExistsAsync())
        {
            await container.CreateAsync();
            await container.SetPermissionsAsync(new BlobContainerPermissions
            {
                PublicAccess = BlobContainerPublicAccessType.Blob
            });
        }

        return container;
    }
}

Hope this helps.

Answer 3

In Azure Storage Client Library 4.0, the get Reference method must be changed to accept relative addresses and nothing else . So, this does not support the libraries earlier than that,

you should change it to either to the blob name or you should use the CloudBlockBlob constructor that takes an Uri and a StorageCredentials object.