azure function: set blob filename from http request - azure

Question

I am trying to set an azure function to upload a blob from an HTTP request to a blob.
I was able to use the following for uploading a file with a static filename:
public static class Uploader
{
[FunctionName("Uploader")]
public static IActionResult Run(
[HttpTrigger(AuthorizationLevel.Function, "post", Route = null)]HttpRequest req,
[Blob("hello/uploaded.jpg", FileAccess.Write)]Stream writer,
TraceWriter log
)
{
log.Info("trigger for image upload started...");
if (!req.ContentType.Contains("multipart/form-data") || (req.Form.Files?.Count ?? 0) == 0)
{
log.Warning("no images found on upload attempt");
return new BadRequestResult();
}
foreach (var file in req.Form.Files)
file.CopyTo(writer.);
return new OkObjectResult("Done!");
}
}
Is there any way I could alter Blob("hello/uploaded.jpg") into something like Blob("hello/{fileName}" to get the name dynamically the HTTP request. I don't mind if it's anywhere from the head or body. I am trying to not use the whole GetBlockBlobReference process just for the dynamic file name alone.
Update
I am not sure if I am missing something or looking at this problem the wrong way. For a serverless set up with a blob storage isn't an HTTP upload supposed to be an obvious and common scenario? How come there aren't any examples for this?

Answer 1

The option suggested by #RomanKiss should work. Alternatively, if you want you can put filename into the function URL template:
[FunctionName("Uploader")]
public static IActionResult Run(
[HttpTrigger(AuthorizationLevel.Function, "post", Route = "uploader/{filename}")]
HttpRequest req,
string filename,
[Blob("hello/{filename}", FileAccess.Write)] Stream writer,
TraceWriter log)
{
//...
}

Answer 2

the following is an example with both an HttpRequestMessage and a POCO binding:
[FunctionName("Uploader")]
public static IActionResult Run(
[HttpTrigger(AuthorizationLevel.Function, "post", Route = null)] Info input, HttpRequest req,
[Blob("hello/{FileName}", FileAccess.Write)]Stream writer,
TraceWriter log
)
{
//...
}
public class Info
{
public string FileName { get; set; }
//...
}
Update:
The following snippet shows an example for using an expanding HttpTrigger binding data support with a well-known properties such as headers and query, more details here:
[FunctionName("Uploader")]
public static IActionResult Run(
[HttpTrigger(AuthorizationLevel.Function, "post", Route = null)HtpRequest req,
[Blob("hello/{query.filename}", FileAccess.Write)] Stream writer,
// [Blob("hello/{headers.filename}", FileAccess.Write)] Stream writer,
TraceWriter log)
{
//...
}
sample of url:
http://localhost:7071/api/Uploader?filename=uploaded.jpg