title: VS doesn't recognize any assemblies in MVC views
body: <p>I'm on Visual Studio 2015 Professional, MVC 5, EF 6, .NET 4.6. I have a solution with several projects, two of which are web projects. VS will sometimes stop recognizing all assemblies in the views of one or both projects. This happens several times each day at what appear to be completely random times. It has happened before where I had nothing open in VS except a view, then I accidentally closed it, immediately reopened it, and the assemblies failed to load upon reopening. I changed nothing, VS simply stopped recognizing them. Controllers work as normal, and the project builds and runs without issue, but it's difficult to not have IntelliSense if only because the entire document is filled with red squiggles.</p>
  
  <p>I have resolved this problem in the past by uninstalling/reinstalling both MVC and WebPages with NuGet, but that hasn't worked this time. Closing VS and clearing both <code>Temporary ASP.NET Files</code> folders had no effect. Both Web.config files are exactly the same as a colleague's; he does not have this problem. I triple checked that all of these assemblies are actually referenced, and <code>Copy Local</code> is <code>true</code> for every single reference in the entire solution. This project was not upgraded to MVC 5, it has always been on MVC 5.</p>
  
  <p>I'm out of ideas. How can I fix the current problem and get VS to not do it in the future?</p>
  
  <p>Some of the specific errors:</p>
  
  <ul>
  <li><code>The type or namespace name 'Linq' does not exist in the namespace 'System' (are you missing an assembly reference?)</code></li>
  <li><code>The type or namespace name 'Helpers' does not exist in the namespace 'System.Web' (are you missing an assembly reference?)</code></li>
  <li><code>The type 'WebViewPage&lt;&gt;' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.</code></li>
  <li><code>'_Page_Views_User__CreateOrUpdate_cshtml.Execute()': no suitable method found to override</code></li>
  </ul>