Write binary data to a blob in an Azure HttpTrigger function

Question

I have an Azure HttpTrigger function that use and IBinder to write data to a blob. It works fine for text data that's posted to my function but binary data not valid when written to the blob. I have code similar to what I've seen in other posts and blogs writing, e.g.

public static async Task<IActionResult> Run(
   [HttpTrigger(AuthorizationLevel.Function, "post", Route = "FileDelivery")] HttpRequest httpRequest,
   IBinder myBinder,
   ILogger log)


...

    using (var writer = myBinder.Bind<TextWriter>(new BlobAttribute(
        $"my-files/{filename}", FileAccess.Write)))
        {
            await writer.WriteAsync(await new StreamReader(httpRequest.Body).ReadToEndAsync());
        };

I think the problem is in the TextWriter being used to bind to the blob. I tried to use a BinaryWriter but got the error Can't bind Blob to type 'System.IO.BinaryWriter. No post I've found has described saving binary data to a blob in this way. Is there a blob attribute I'm missing or some other setting that will get this to work?

Frank Gong Frank Gong · Accepted Answer · 2021-03-17T02:54:42

I think you can use the following parameter types, you can refer to this documentation:

The following code is an example of how I accept an image and upload it to storage:

            using (var destinationStream = myBinder.Bind<Stream>(new BlobAttribute(
                $"test/test.jpg", FileAccess.Write)))
                {
                var image = req.Form.Files["test"];
                await image.CopyToAsync(destinationStream);
                };

This is my request body:

Write binary data to a blob in an Azure HttpTrigger function

1 Answers