title: Download file prompt when using WebAPI HttpResponseMessage
body: <p>I have a method in my API that returns a HttpResponseMessage:</p>
  
  <pre><code>    [HttpGet, HoodPeekAuthFilter]
      public HttpResponseMessage GlobalOverview()
      {
          try
          {
              StatsRepo _statsRepo = new StatsRepo();
  
              string file = _statsRepo.IncidentData().AsCSVString();
  
              if (file == null)
              {
                  return Request.CreateResponse(HttpStatusCode.NoContent);
              }
  
              HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);
              result.Content = new StringContent(file);
              result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
              result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
              result.Content.Headers.ContentDisposition.FileName = "GlobalOverview.csv";
  
              return result;
          }
          catch (Exception ex)
          {
              return Request.CreateResponse(HttpStatusCode.InternalServerError);
          }
      }
  </code></pre>
  
  <p>In my MVC Web Apllication i have a controller Action that needs to call the API and return the file:</p>
  
  <pre><code>    [Authorize]
      [HttpGet]
      public HttpResponseMessage GlobalOverview()
      {
          HttpResponseMessage file = new HttpResponseMessage();
          using (HttpClient httpClient = new HttpClient())
          {
              httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(UTF8Encoding.UTF8.GetBytes(this.UserName + ':' + this.Password)));
              Task&lt;HttpResponseMessage&gt; response = httpClient.GetAsync("api.someDomain/Reporting/GlobalOverview");
              file = response.Result;
          }
  
          return file;
      }
  </code></pre>
  
  <p>If i access the API url directly it prompts me for a username and password, and then the Save File dialogue appears, and i can download the file.</p>
  
  <p>If i navigate to the Action in my Web Application then i get the following response output to screen: </p>
  
  <pre><code>StatusCode: 200, 
  ReasonPhrase: 'OK', 
  Version: 1.1, 
  Content: System.Net.Http.StreamContent, 
  Headers: { Pragma: no-cache X-SourceFiles: = XXXXXXX
  Content-Disposition: attachment; 
  filename=GlobalOverview.csv 
  Content-Type: application/octet-stream Expires: -1 
  </code></pre>
  
  <p>I take it i need to return a FileResult, but i have no clue as to how to convert the HttpResponseMessage to a FileResult.</p>