title: Unrecognized tag prefix or device filter 'asp' after upgrading to VS2012
body: <p>I upgraded a Visual Studio 2010 Class Library project to 2012.  This project contains several web user controls.  After the upgrade, all of my ascx files show the error "Unrecognized tag prefix or device filter 'asp'" for every asp.net control in use.</p>
  
  <p>I have tried deleting my roaming profile folders, <a href="https://stackoverflow.com/questions/3772901/visual-studio-2010-conversion-issue-not-recognizing-prefix-asp">as suggested here</a>.</p>
  
  <p>I previously had no web.config file, but I tried adding one so that I could add and remove the <a href="https://stackoverflow.com/questions/12809653/unrecognized-tag-prefix-or-device-filter-asp-in-vs2012">entries described here</a>.</p>
  
  <p>If I add a <strong>new</strong> user control to my project, then symbols resolve correctly.</p>
  
  <p>Does anyone have an alternative approach to resolving this?</p>