ASP.NET MVC 5 and Visual Studio 2015RC CS0234 errors

There are similar Qs on SO but I could find none relating to my specifics

The ASP.NET MVC out of the box templates build and run ok but in the editor I have red squigglies all over the place with 17 CS0234 errors each reporting:

"the name xxxx does not exist in the current context"

Where xxxx is ViewBag, Scripts, RenderSection etc.

Observe same issue with opening existing projects from vs2013 in 2015.

I have tried deleting and reinstalling MVC (Microsoft.AspNet.Mvc) manually using nuget to no avail.

os: windows 8.1 pro

Maybe a known bug? Hope someone can throw some light on this.

Web Config (extract):

<dependentAssembly>
    <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
    <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
  </dependentAssembly>
  <dependentAssembly>
    <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
    <bindingRedirect oldVersion="1.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
  </dependentAssembly>
  <dependentAssembly>

Packages (extract):

<packages>

  <package id="Microsoft.AspNet.Identity.Core" version="2.2.0" targetFramework="net452" userInstalled="true" />
  <package id="Microsoft.AspNet.Identity.EntityFramework" version="2.2.0" targetFramework="net452" userInstalled="true" />
  <package id="Microsoft.AspNet.Identity.Owin" version="2.2.0" targetFramework="net452" userInstalled="true" />
  <package id="Microsoft.AspNet.Mvc" version="5.2.3" targetFramework="net452" userInstalled="true" />
  <package id="Microsoft.AspNet.Razor" version="3.2.3" targetFramework="net452" userInstalled="true" />
  <package id="Microsoft.AspNet.Web.Optimization" version="1.1.3" targetFramework="net452" userInstalled="true" />
  <package id="Microsoft.AspNet.WebPages" version="3.2.3" targetFramework="net452" userInstalled="true" />

</packages>