title: Type missing when Asp.net MVC4 website starts
body: <p>When I start an Asp.net MVC4 website in visual studio 2012. I was stuck with an exception said :</p>
  
  <pre><code>Could not load type 'System.Net.Http.Formatting.DefaultContentNegotiator' 
  from assembly 'System.Net.Http.Formatting, Version=4.0.0.0, Culture=neutral,
  PublicKeyToken=31bf3856ad364e35'.
  </code></pre>
  
  <p>On the code :</p>
  
  <pre><code>routes.MapHttpRoute(
                  name: "DefaultApi",
                  routeTemplate: "api/{controller}/{id}",
                  defaults: new { id = System.Web.Http.RouteParameter.Optional }
              );
  </code></pre>
  
  <p>the Whole code looks like :</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Web;
  using System.Web.Mvc;
  using System.Web.Routing;
  using System.Web.Http;
  
  
  namespace Accela.Apps.Diagnostics.Portal
  {
      public class RouteConfig
      {
          public static void RegisterRoutes(RouteCollection routes)
          {
              routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
  
              routes.MapHttpRoute(
                  name: "DefaultApi",
                  routeTemplate: "api/{controller}/{id}",
                  defaults: new { id = System.Web.Http.RouteParameter.Optional }
              );
  
  
              routes.MapRoute(
                 name: "Default",
                 url: "{controller}/{action}/{id}",
                 defaults: new { controller = "Login", action = "Login", id = UrlParameter.Optional }
             );
          }
      }
  }
  </code></pre>
  
  <p>Please help get me out of there.thanks.</p>