Inheritance security rules violated by type: ‘System.Web.Mvc.MvcWebRazorHostFactory’. Derived types must either match the security accessibility of the base type or be less accessible.
Search your whole solution for references to MvcWebRazorHostFactory
<host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
Change it to:
<host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=5.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />