Download file request returning JSON instead of file in ASP.NET Web API on server

Question

I'm trying to download CSV file in ASP.NET Web API. Here is my code, and it's working in local.

[Route("{name?}")]
public HttpResponseMessage Get(string name = "DownloadFile")
{
    name = name.EndsWith(".csv") ? name : $"{name}.csv";
    var stream = new MemoryStream();
    var writer = new StreamWriter(stream);
    writer.Write("Hello, World!");
    writer.Flush();
    stream.Position = 0;

    var result = new HttpResponseMessage(HttpStatusCode.OK)
    {
        Content = new ByteArrayContent(stream.ToArray())
    };
    result.Content.Headers.Add("x-filename", name);
    result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
    result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
    {
        FileName = name
    };
    return result;
}

The file is being downloaded in browser in localhost. I deployed the same code on the server and it's returning a JSON in the browser instead of downloading a file.

JSON looks like this:

{
  "version": {
    "major": 1,
    "minor": 1,
    "build": -1,
    "revision": -1,
    "majorRevision": -1,
    "minorRevision": -1
  },
  "content": {
    "headers": [
      {
        "key": "x-filename",
        "value": [
          "test.csv"
        ]
      },
      {
        "key": "Content-Type",
        "value": [
          "application/octet-stream"
        ]
      },
      {
        "key": "Content-Disposition",
        "value": [
          "attachment; filename=test.csv"
        ]
      }
    ]
  },
  "statusCode": 200,
  "reasonPhrase": "OK",
  "headers": [],
  "requestMessage": null,
  "isSuccessStatusCode": true
}

I've checked mime type in IIS and it's there. Am I missing anything ??

Answer 1

I ran into this similar problem using WebApi which worked fine locally when debugging in Visual Studio and when deployed to IIS locally. On my server, I was getting the JSON response as above. After a fresh deploy I was seeing a new error about missing method:

Method not found: 'System.Net.Http.HttpRequestMessage System.Web.Http.Controllers.HttpActionContext.get_Request()'.

The resolution was to add a new binding redirect. Perhaps this is an effective fix for you.

  <dependentAssembly>
    <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
    <bindingRedirect oldVersion="0.0.0.0-4.0.0.0" newVersion="4.2.0.0" />
  </dependentAssembly>