In .NET MVC 4 (Web API), how do I intercept a request for a controller and change it's Content-Type?

Question

Thanks for looking!

Background

I am writing an API layer for a company that will be used by disparate apps and external consumers.

On the consumption end, most consumers will call a service via ajax using a jQuery $.post(); however, Internet Explorer makes our lives more challenging (of course!). For IE, I must use the XDomainRequest object because IE will not run a jQuery $.post() and because if I use IE's XMLHttpRequest(), I get a security message which is unacceptable (again--of course!):

Otherwise, XMLHttpRequest() works fine.

I am using C#, .NET MVC 4 (WebApi)

Problem

The problem is that XDomainRequest does not allow you to set the Content-Type header and always defaults to text-plain which MVC 4 WebApi controllers will not accept (and yet again--of course!!).

Question

How can I intercept requests for my controllers, detect the presence of text-plain content types and change them to text-json content-type on the fly?

Thanks in advance!

Answer 1

Well after two days and pouring over documentation and reading in this thread I've been able to make this work. So please forgive me if my description of the solution is poor; this is the first time I answer one of these types of threads. Since it took me so long to find the problem I figured it is worth saving some soul from falling into this same problem.

The source for my help came from the above link by byterot.

1. First thing I did was to create a DelegatingHandler. So in my helper folder or where every you want to create a class and call it what you want.
   Here is mine:

   public class ContentTypeHandler : DelegatingHandler
   {
       /** Check that this is an IE browser. */
       if ((request.Headers.UserAgent.ToString().IndexOf("MSIE", System.StringComparison.Ordinal) > -1))
       {
           MediaTypeHeaderValue contentTypeValue;
           if (MediaTypeHeaderValue.TryParse("application/json", out contentTypeValue))
           {
               request.Content.Headers.ContentType = contentTypeValue;
               request.Content.Headers.ContentType.CharSet = "utf-8";
           }
       }
   
       /** Return request to flow. */
       return base.SendAsync(request, cancellationToken)
          .ContinueWith(task =>
          {
               // work on the response
               var response = task.Result;
               return response;
          });
   }
   

2. Last think that you have to do is call the Handler in your Global.asax.cs file inside your Application_Start():

   GlobalConfiguration.Configuration.MessageHandlers.Add(new ContentTypeHandler());
   

That's all I did and it worked. So good luck I hope this helps someone.

Answer 2

There is no problem modifying request in HTTP stack. It can be done by writing and registering your custom DelegatingHandler before it gets to the controller. Delegating handler can take care of this early-on in the game, so your request will arrive to the controller in the form you want it to. It could be route-specific handler as well. http://msdn.microsoft.com/en-us/library/system.net.http.delegatinghandler.aspx

Did you try $.ajax instead of $.post ?