This post is a small cry for help along with an explanation of a problem that is hard to describe on twitter or even a connect bug and written in hopes somebody has seen this before and any ideas on what might cause this. Lots of helpful people had comments on Twitter for me, but they all assumed that the code doesn't run, which is not the case - it's a designer issue.

A few days ago I started getting some odd problems in my MVC 4 designer for an app I've been working on for the past 2 weeks. Basically the MVC 4 Razor designer keeps popping me errors, about the call signature to various Html Helper methods being incorrect. It also complains about the ViewBag object and not supporting dynamic requesting to load assemblies into the project.

Here's what the designer errors look like:

MVC Errors

You can see the red error underlines under the ViewBag and an Html Helper I plopped in at the top to demonstrate the behavior. Basically any HtmlHelper I'm accessing is showing the same errors.

Note that the code *runs just fine* - it's just the designer that is complaining with Errors.

What's odd about this is that *I think* this started only a few days ago and nothing consequential that I can think of has happened to the project or overall installations. These errors aren't critical since the code runs but pretty annoying especially if you're building and have .csHtml files open in Visual Studio mixing these fake errors with real compiler errors.

What I've checked

Looking at the errors it indeed looks like certain references are missing. I can't make sense of the Html Helpers error, but certainly the ViewBag dynamic error looks like System.Core or Microsoft.CSharp assemblies are missing. Rest assured they are there and the code DOES run just fine at runtime. This is a designer issue only.

I went ahead and checked the namespaces that MVC has access to in Razor which lives in the Views folder's web.config file:


For good measure I added

    <host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc,  <split for layout>
Version=, Culture=neutral, PublicKeyToken=31BF3856AD364E35
" /> <pages pageBaseType="System.Web.Mvc.WebViewPage"> <namespaces> <add namespace="System.Web.Mvc" /> <add namespace="System.Web.Mvc.Ajax" /> <add namespace="System.Web.Mvc.Html" /> <add namespace="System.Web.Routing" /> <add namespace="System.Linq" /> <add namespace="System.Linq.Expressions" /> <add namespace="ClassifiedsBusiness" /> <add namespace="ClassifiedsWeb"/> <add namespace="Westwind.Utilities" /> <add namespace="Westwind.Web" /> <add namespace="Westwind.Web.Mvc" /> </namespaces> </pages> </system.web.webPages.razor>

For good measure I added System.Linq and System.Linq.Expression on which some of the Html.xxxxFor() methods rely, but no luck.

So, has anybody seen this before? Any ideas on what might be causing these issues only at design time rather, when the final compiled code runs just fine?