Azure Function Blob Storage connection: The format of value '*' is invalid

Question

I am writing a v2 Azure Function in which I will access Azure Blob Storage. Because I was having trouble, I reduced it down to this minimal example.

namespace Test
{
    public static class Function1
    {
        [FunctionName("Function1")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "test")] HttpRequest req,
            ILogger log)
        {
            var azureStorage = CloudStorageAccount.Parse("UseDevelopmentStorage=true");
            var blobClient = azureStorage.CreateCloudBlobClient();
            var container = blobClient.GetContainerReference("migrated-load-sets-localhost");
            var blobReference = container.GetBlockBlobReference("11016093-2f6e-4631-97c1-04f8acfb2370");
            var memoryStream = new MemoryStream();
            var accessCondition = AccessCondition.GenerateIfExistsCondition();
            var blobRequestOptions = new BlobRequestOptions();
            await blobReference.DownloadToStreamAsync(memoryStream, accessCondition, blobRequestOptions, null);
            var text = System.Text.Encoding.UTF8.GetString(memoryStream.ToArray());
            return new OkObjectResult(text);
        }
    }
}

When I run and hit this, I get the error

System.Private.CoreLib: Exception while executing function: Function1. Microsoft.WindowsAzure.Storage: The format of value '*' is invalid. System.Net.Http: The format of value '*' is invalid.

If I change

var accessCondition = AccessCondition.GenerateIfExistsCondition();

to be

var accessCondition = AccessCondition.GenerateEmptyCondition();

it works.

I have observed in debugging that accessCondition.IfMatchETag equals "*" , so it seems like that might be the culprit.

Am I doing something wrong when I use AccessCondition.GenerateIfExistsCondition() , or is there a bug in the library?

Answer 1

In case if you need to check if the blob is present before downloading the file , all you need is

if(blobReference.ExistsAsync())
{
   //Download
}