title: MVC5 with VB.NET: "BC30451: 'ViewData' is not declared." when switching to Debug configuration
body: <p>I have a MVC5 project that is currently set on the "Release Configuration" and it works 100%.  However, as soon as I switch the project configuration from Release to Debug, then everything goes wrong... even if I switch it back to Release mode, everything is still broken.  Only way I can get the project working again is to restore from a backup.</p>
  
  <p>Here are what is happening.
  Firstly, when running the project, I get the following error:</p>
  
  <blockquote>
    <p>BC30451: 'ViewData' is not declared. It may be inaccessible due to its
    protection level.</p>
  </blockquote>
  
  <p>If I open any view in the project with Visual Studio 2013, I can see that all sorts of things are marked as errors like ViewData, Html, Url, etc.</p>
  
  <p>When referring to @Html or @ViewData in the view, it normally refers to the .Html and .ViewData properties of the view's base class (WebViewPage).  However, if I start typing "@Html." in any of the views, I can see in the autocomplete that it is referring to the System.Web.Webpages.Html namespace instead of the WebViewPage.Html property.  It is as-if the view isn't inheriting from the System.Web.Mvc.WebViewPage class.</p>
  
  <p>Any guidance as to where I can start looking to get this fixed or why this is happening?</p>
  
  <p><b><i>Edit:</i></b>
  So since nobody responded, I went through the long way.  I created a brand new MVC5 project, added all the packages via Nuget and then simply copied all my files over from the old project to the new one and now it works.</p>
  
  <p>Does anybody have any idea what the heck could be causing this?  I don't want to go through all this trouble again in the future if the project again suddenly decides to stop working.</p>