MVC 6 WebAPI returns serialized HttpResponseMessage instead of file stream

Question

I'm trying to make my ASP.Net 5 MVC 6 WebAPI project output a file, in response to a HttpGET request.

The file is from an Azure Files share, but it could be any stream containing a binary file.

It seems to me that MVC serializes the response object, and returns the resulting JSON, rather than returning the response object itself.

Here is my controller method:

    [HttpGet]
    [Route("GetFile")]
    public HttpResponseMessage GetFile(string Username, string Password, string FullName)
    {

        var client = new AzureFilesClient.AzureFilesClient(Username, Password);
        Stream azureFileStream =  client.GetFileStream(FullName).Result;
        var fileName = Path.GetFileName(FullName);

        using (HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK))
        {
            response.Content = new StreamContent(azureFileStream);
            response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
            response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment") { FileName = fileName };
            return response;
        }
    }

The GetFileStream method on the AzureFilesClient is here, though the stream source could be anything containing binary file content:

    public async Task<Stream> GetFileStream(string fileName)
    {
        var uri = new Uri(share.Uri + "/" + fileName);
        var file = new CloudFile(uri, credentials);

        using (var stream = new MemoryStream())
        {
            await file.DownloadToStreamAsync(stream);
            stream.Seek(0, SeekOrigin.Begin);
            return stream;
        }
    }

Edit: Here is a sample of the JSON response:

{
    "Version": {
        "Major": 1,
        "Minor": 1,
        "Build": -1,
        "Revision": -1,
        "MajorRevision": -1,
        "MinorRevision": -1
    },
    "Content": {
        "Headers": [
            {
                "Key": "Content-Type",
                "Value": [
                    "application/octet-stream"
                ]
            },
            {
                "Key": "Content-Disposition",
                "Value": [
                    "attachmentx; filename=\"samplefile.docx\""
                ]
            }
        ]
    },
    "StatusCode": 200,
    "ReasonPhrase": "OK",
    "Headers": [],
    "RequestMessage": null,
    "IsSuccessStatusCode": true
}

Answer 1

After a combination of reading documentation aswell as some trial and error, the problems have been solved.

The Azure part was made using the nuGet package "WindowsAzure.Storage" (4.4.1-preview)

First the output that got JSON serialized. That required a custom action result to be returned instead.

using Microsoft.AspNet.Mvc;
using System.IO;
using System.Threading.Tasks;

public class FileResultFromStream : ActionResult
{
    public FileResultFromStream(string fileDownloadName, Stream fileStream, string contentType)
    {
        FileDownloadName = fileDownloadName;
        FileStream = fileStream;
        ContentType = contentType;
    }

    public string ContentType { get; private set; }
    public string FileDownloadName { get; private set; }
    public Stream FileStream { get; private set; }

    public async override Task ExecuteResultAsync(ActionContext context)
    {
        var response = context.HttpContext.Response;
        response.ContentType = ContentType;
        context.HttpContext.Response.Headers.Add("Content-Disposition", new[] { "attachment; filename=" + FileDownloadName });
        await FileStream.CopyToAsync(context.HttpContext.Response.Body);
    }
}

Now for getting the binary data streamed from an Azure files share (or any other async stream source)

using Microsoft.WindowsAzure.Storage;
using Microsoft.WindowsAzure.Storage.Auth;
using Microsoft.WindowsAzure.Storage.File;
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Threading.Tasks;

    public async Task<Stream> GetFileStreamAsync(string fileName)
    {
        var uri = new Uri(share.Uri + "/" + fileName);
        var file = new CloudFile(uri, credentials);

        // Note: Do not wrap the stream variable in a Using, since it will close the stream too soon.
        var stream = new MemoryStream();
        await file.DownloadToStreamAsync(stream);
        stream.Seek(0, SeekOrigin.Begin);
        return stream;
    }

And finally the controller code. Note the use of the IActionResult interface.

    [HttpGet]
    [Route("GetFile")]
    public async Task<IActionResult> GetFile(string username, string password, string fullName)
    {
        var client = new AzureFilesClient.AzureFilesClient(username, password);
        Stream stream = await client.GetFileStreamAsync(fullName);
        string fileName = Path.GetFileName(fullName);
        return new CustomActionResults.FileResultFromStream(fileName, stream, "application/msword");
    }

Note: This example is only used with Word files, you might want to look into making the ContentType parameter dynamic, instead of static like this.