Azure Blob Upload not working in ASP .Net Core Application

I am trying to upload a file to Azure blob storage in Asp .Net Core. Everything seems to be working but no file is uploaded. Here is my code snippet:

var blobReference = GetBlobReference();
rawData.Position = 0;

// var result = blobReference.UploadFromStreamAsync(rawData);
var result = blobReference.UploadFromFileAsync("C:\users\tjaartb\Downloads\DebitOrderMandate.pdf");
result.GetAwaiter().GetResult();
var blobPath = blobReference.Uri.ToString();


The debugger steps over the result.GetAwaiter().GetResult() with no exceptions occurring. Checking the result Task variable after the GetResult() call shows that the task state is RanToCompletion and the exception property is blank. My blob container is created successfully in earlier code indicating that the connection to blob storage is successful. GetResult() finishes instantly, so it seems like nothing is happening.

result.GetAwaiter().GetResult()

result

GetResult()

RanToCompletion

GetResult()

rawData

MemoryStream

Started Thread <ThreadNumber>

blobReference.UploadFromFileAsync()

FileNotFoundException

netcoreapp2.0

netcoreapp2.1

await blobReference.UploadFromFileAsync("C:\users\tjaartb\Downloads\DebitOrderMandate.pdf");

await blobReference.UploadFromFileAsync("C:\users\tjaartb\Downloads\DebitOrderMandate.pdf");

4 Answers
4

the following code with WindowsAzure.Storage - Version 9.3.1 package works on Asp Net Core 2.1.

public class AzureBlobModel

public string FileName get; set;
public long? FileSize get; set;
public Stream Stream get; set;
public string ContentType get; set;


public interface IImageStore

Task<string> SaveDocument(Stream documentStream);
Task<bool> DeleteDocument(string imageId);
Task<AzureBlobModel> DownloadDocument(string documentId, string fileName);
string UriFor(string documentId);


public class ImageStore : IImageStore

CloudBlobClient blobClient;
string baseUri = "https://xxxxx.blob.core.windows.net/";

public ImageStore()

var credentials = new StorageCredentials("xxxxx accountName xxxxx", "xxxxx keyValue xxxxx");
blobClient = new CloudBlobClient(new Uri(baseUri), credentials);


public async Task<string> SaveDocument(Stream documentStream)

var documentId = Guid.NewGuid().ToString();
var container = blobClient.GetContainerReference("xxxxx container xxxxx");
var blob = container.GetBlockBlobReference(documentId);
await blob.UploadFromStreamAsync(documentStream);
return documentId;


public async Task<bool> DeleteDocument(string documentId)

var container = blobClient.GetContainerReference("xxxxx container xxxxx");
var blob = container.GetBlockBlobReference(documentId);
bool blobExisted = await blob.DeleteIfExistsAsync();
return blobExisted;


public async Task<AzureBlobModel> DownloadDocument(string documentId, string fileName)

var container = blobClient.GetContainerReference("xxxxx container xxxxx");
var blob = container.GetBlockBlobReference(documentId);

var doc = new AzureBlobModel()

FileName = fileName,
Stream = new MemoryStream(),
;

doc.Stream = await blob.OpenReadAsync();
doc.ContentType = blob.Properties.ContentType;
doc.FileSize = blob.Properties.Length;

return doc;


public string UriFor(string documentId)

var sasPolicy = new SharedAccessBlobPolicy

Permissions = SharedAccessBlobPermissions.Read,
SharedAccessStartTime = DateTime.UtcNow.AddMinutes(-15),
SharedAccessExpiryTime = DateTime.UtcNow.AddDays(1)
;

var container = blobClient.GetContainerReference("xxxxx container xxxxx");
var blob = container.GetBlockBlobReference(documentId);
var sas = blob.GetSharedAccessSignature(sasPolicy);
return $"baseUrixxxxx container xxxxx/documentIdsas";



public class DocForCreationDto

public IFormFile File get; set;

// other properties ...


// On the controller

[HttpPost]
public async Task<IActionResult> Upload([FromForm]DocForCreationDto docForCreationDto)
!ModelState.IsValid)

return new UnprocessableEntityObjectResult(ModelState);


string documentId = string.Empty;
using (var stream = docForCreationDto.File.OpenReadStream())

documentId = await _imageStore.SaveDocument(stream);


if (documentId != string.Empty)

// upload ok ...
//some business logic here ...
return Ok();


return BadRequest("xxx error xxx");


[HttpGet("documentId", Name = "GetDocument")]
public async Task<IActionResult> GetDocument(int documentId)

var doc = await _imageStore.DownloadDocument(documentId, "output filename");

return File(doc.Stream, doc.ContentType, doc.FileName);


// On Startup - ConfigureServices

services.AddSingleton<IImageStore, ImageStore>();


The interface I am implementing in that method is part of a larger ecosystem that doesn't have async signatures. It would require a lot of effort to refactor it.

You could use Wait() to replace await to implement the async signatures.Refer to the following code:

Wait()

await

CloudStorageAccount storageAccount = CloudStorageAccount.Parse(connection);
CloudBlobClient cloudBlobClient = storageAccount.CreateCloudBlobClient();
var cloudBlobContainer = cloudBlobClient.GetContainerReference("containername");
CloudBlockBlob blob = cloudBlobContainer.GetBlockBlobReference("DebitOrderMandate.pdf");
using (var fileStream = System.IO.File.OpenRead("C:\users\tjaartb\Downloads\DebitOrderMandate.pdf"))

blob.UploadFromStreamAsync(fileStream).Wait();



Adding a / prefix to a Blob name results in a silent failure. The file does not upload at all. removing the / prefix fixed the problem.

/

/

With .NET Core 2.1 and WindowsAzure.Storage 9.3.2 all the methods are now async. If you don't await all the async method calls you can get silent failures. The comments below the question helped me figure that out.

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