title: HttpResponseMessage unavailable in App_Code folder of VS 2012 project
body: <p>I am writing a Web API project (MVC architecture).  I have a utility class with methods that returns an HttpResponseMessage.  If this class is placed in a Utility folder everything works.  If I attempt to place the class within the App_Code folder, I receive the message "The type or namespace name 'HttpResponseMessage' found not be found."</p>
  
  <p>An example of a method that this occurs with is provided below.  What needs to be done to be able to declare a variable or method as HttpResponseMessage within the App_Code folder?</p>
  
  <pre><code>    public HttpResponseMessage GetResponseMessage&lt;T&gt;(T item, MediaTypeFormatter mtFormatter)
      {
          HttpResponseMessage response = new HttpResponseMessage()
          {
              Content = new ObjectContent&lt;T&gt;(item, mtFormatter)
          };
  
          return response;
      }
  </code></pre>