title: After Windows update "The type or namespace name 'Html' does not exist in the namespace 'System.Web.Mvc'"
body: <p>I did a Windows update and afterwards my asp.net mvc 5 application will no longer load complaining about </p>
  
  <pre><code>CS0234: The type or namespace name 'Html' does not exist in the namespace 'System.Web.Mvc'
  </code></pre>
  
  <p>indicating my views web.config is at fault</p>
  
  <pre><code>  &lt;system.web.webPages.razor&gt;
      &lt;host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=5.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
      &lt;pages pageBaseType="System.Web.Mvc.WebViewPage"&gt;
        &lt;namespaces&gt;
          &lt;add namespace="System.Web.Mvc" /&gt;
          &lt;add namespace="System.Web.Mvc.Ajax" /&gt;
          &lt;add namespace="System.Web.Mvc.Html" /&gt;
          &lt;add namespace="System.Web.Optimization"/&gt;
          &lt;add namespace="System.Web.Routing" /&gt;
          &lt;add namespace="Ogre.Extensions" /&gt;
          &lt;add namespace="Newtonsoft.Json"/&gt;
        &lt;/namespaces&gt;
      &lt;/pages&gt;
    &lt;/system.web.webPages.razor&gt;
  </code></pre>
  
  <p>Now this is very confusing. In my project itself I can see the <code>Html</code> namespace, opening my assembly in ILSpy I can navigate to the bound <code>System.Web.Mvc</code> and I can it as well, and the fusion log is not showing any suspicious binding errors. </p>
  
  <p>It's as if <em>just</em> my views are getting bound (successfully) to an old version of Mvc. Why would that ever happen? How can I fix it?</p>
  
  <p>Let me be clear that there have been no configuration or even code changes. This is all on my dev machine on IISExpress. It was running, I did the update and rebooted and now it is no longer running.</p>
  
  <p>Here are my recent installs from the update. I could start removing them one by one, but I want to know what is actually going wrong as it feels like I'm missing part of the story.</p>
  
  <p><img src="https://i.stack.imgur.com/FUANR.png" alt="Installs from the update"></p>