title: CS0234: Mvc does not exist in the System.Web namespace
body: <p>I converted a ASP.net 4 webform project to Asp.net MVC4 according to Chapter 13 of the Professional ASP.NET 3.5 MVC, by Scott Hanselmen, Phil Haack, and Rob Conery, Published by Wiley Publishing, Inc. (ISBN: 978-0-470-38461-9).  I also followed this <a href="http://www.britishdeveloper.co.uk/2011/05/convert-web-forms-mvc3-how-to.html">blog</a>.  Now I can add Controllers, Views, etc. All the references are set properly. No build errors.  But upon launching the converted project, I got compilation errors.  I have mvc3 installed on the same machine. I even changed the reference to that. It still complain.  Could you help?  Thanks.</p>
  
  <pre><code>Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately. 
  
  Compiler Error Message: CS0234: The type or namespace name 'Mvc' does not exist in the namespace 'System.Web' (are you missing an assembly reference?)
  
  Source Error:
  
  Line 109:            &lt;namespaces&gt;
  Line 110:                &lt;add namespace="System.Web.Helpers"/&gt;
  Line 111:                &lt;add namespace="System.Web.Mvc"/&gt;
  Line 112:                &lt;add namespace="System.Web.Mvc.Ajax"/&gt;
  Line 113:                &lt;add namespace="System.Web.Mvc.Html"/&gt; 
  
  Source File: c:\Users\Jon\Documents\Visual Studio 2012\Projects\CMT\Apps\Branches\3.0\Web.config    Line: 111 
  </code></pre>