title: The type 'System.Web.WebPages.HelperResult' exists in both
body: <p>I have an umbraco site and looks like I have two versions of mvc running on a site, how do I fix this error? I can't see any duplicate references that are exactly the same in the project references.</p>
  
  <blockquote>
    <p>CS0433: The type 'System.Web.WebPages.HelperResult' exists in both 'c:\Windows\Microsoft.NET\assembly\GAC_MSIL\System.Web.WebPages\v4.0_2.0.0.0__31bf3856ad364e35\System.Web.WebPages.dll' and 'c:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\21adadbc\1f460423\assembly\dl3\877dcc43\3f192a14_afc4d101\System.Web.WebPages.DLL'</p>
  </blockquote>