Uploading a file in MVC4 C#5 .NET 4.5


Back on the bleeding edge again Hot smile I’m in the early stages of my next killer app and I’m investigating the pros and cons of using the new ASP WebApi.

One of the features of this so called killer app will be to upload pictures (nothing special I agree). But how would I do this for all the clients I hope to support (WinRT/WP7/Html5/IOS).

Let me first present the server that will be used for all these clients, I’ll then follow up with what I consider to be the simplest client a html5 browser!


So I fired up VS11 and created a new MVC4 application using .net 4.5 / C#  and the WebApi template.

I then added a controller called FileUploadController.cs

   1:  using System.Collections.Generic;
   2:  using System.Linq;
   3:  using System.Net;
   4:  using System.Net.Http;
   5:  using System.Threading.Tasks;
   6:  using System.Web.Http;
   8:  namespace MvcApplication16.Controllers
   9:  {
  10:      public class FileUploadController : ApiController
  11:      {
  12:          public async Task<IEnumerable<string>> PostMultipartStream()
  13:          {
  14:              // Check we're uploading a file
  15:              if (!Request.Content.IsMimeMultipartContent("form-data"))            
  16:                  throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
  18:              // Create the stream provider, and tell it sort files in my c:\temp\uploads folder
  19:              var provider = new MultipartFormDataStreamProvider("c:\\temp\\uploads");
  21:              // Read using the stream
  22:              var bodyparts = await Request.Content.ReadAsMultipartAsync(provider);            
  24:              // Create response.
  25:              return provider.BodyPartFileNames.Select(kv => kv.Value);            
  26:          }
  27:      }
  29:  }

You can see from line 12 that I’ve made this operation async, you’ve really got to admire the simplicity of async/await construct in .net 4.5! In line 22 you can see that the compiler and some state machine magic allow the freeing up of the asp worker thread….. (If you have read my previous posts you may be a little confused now.. didn’t I say that Tasks will use use the same threadpool!?  have a look at this link for someone that pondered the very same concerns )


HTML5 Client

The client couldn’t have been easier, fist a look at it in the browser


   1:  <!DOCTYPE html>
   2:  <html lang="en">
   3:  <head>
   4:      <meta charset="utf-8" />
   5:      <title>ASP.NET Web API</title>
   6:      <link href="@Url.Content("~/Content/Site.css")" rel="stylesheet" type="text/css" />
   7:      <meta name="viewport" content="width=device-width" />
   8:  </head>
   9:  <body>
  10:      @using (Html.BeginForm("FileUpload", "api", FormMethod.Post, new { enctype = "multipart/form-data" }))
  11:      { 
  12:          <div>Please select some files</div>
  13:          <input name="data" type="file" multiple>
  14:          <input type="submit" />            
  15:      }
  16:  </body>
  17:  </html>


The important part above is using the enctype attribute, in fact line 10 loosely translates to

<form action="~/api/FileUpload" enctype="multipart/form-data" method="POST">

Don’t believe me? Then try VS11’s awesome new feature – page inspector

Right click on the html and choose view in page inspector




and we’re done! Of course in the real world we’ll use ajax with a few trick re sandbox, but here’s the response in the browser with xml.


I’ll hopefully follow up with the samples for the client list below when I get to the respective development machines.

  • WinRT (c#/xaml)
  • iPhone (objective c)
  • Android (java)

Comments (6) -

  • Loosely translates to ~/api/FileUpload

    BTW nice article Smile
  • hi, its nice article but i face with this error ???

    Error  6  'System.Net.Http.MultipartFormDataStreamProvider' does not contain a definition for 'BodyPartFileNames' and no extension method 'BodyPartFileNames' accepting a first argument of type 'System.Net.Http.MultipartFormDataStreamProvider' could be found (are you missing a using directive or an assembly reference?)  C:\Users\Mahdi\documents\visual studio 2012\Projects\MvcApplication3\MvcApplication3\Controllers\FileUploadController.cs  31  32  MvcApplication3
  • I followed you sample up until the html 5 client.  Not sure how do you make that connection with the controller?
  • I followed you sample up until the html 5 client.  Not sure how do you make that connection with the controller?
  • Ali
    Nice article on uploading image using web API.
  • apologies about the slow replies, my site was getting a lot of spam so comments were all being queued.


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