The error is:
[A]System.Web.WebPages.Razor.Configuration.HostSection cannot be cast to [B]System.Web.WebPages.Razor.Configuration.HostSection. Type A originates from ‘System.Web.WebPages.Razor, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35’ in the context ‘Default’ at location ‘C:\windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.WebPages.Razor\v4.0_2.0.0.0__31bf3856ad364e35\System.Web.WebPages.Razor.dll’. Type B originates from ‘System.Web.WebPages.Razor, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35’ in the context ‘Default’ at location ‘C:\Users\e.rossini\AppData\Local\Temp\Temporary ASP.NET Files\root\55c43b6b\aa340995\assembly\dl3\a83c308f\965a638d_c896cf01\System.Web.WebPages.Razor.dll’.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.InvalidCastException: [A]System.Web.WebPages.Razor.Configuration.HostSection cannot be cast to [B]System.Web.WebPages.Razor.Configuration.HostSection. Type A originates from ‘System.Web.WebPages.Razor, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35’ in the context ‘Default’ at location ‘C:\windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.WebPages.Razor\v4.0_2.0.0.0__31bf3856ad364e35\System.Web.WebPages.Razor.dll’. Type B originates from ‘System.Web.WebPages.Razor, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35’ in the context ‘Default’ at location ‘C:\Users\e.rossini\AppData\Local\Temp\Temporary ASP.NET Files\root\55c43b6b\aa340995\assembly\dl3\a83c308f\965a638d_c896cf01\System.Web.WebPages.Razor.dll’.
The solution
Add this in the web.config
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentAssembly>
<assemblyIdentity name="System.Web.WebPages.Razor" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="0.0.0.0-3.0.0.0" newVersion="3.0.0.0"/>
</dependentAssembly>
</assemblyBinding>
</runtime>
