http://stackoverflow.com/questions/22793322/asystem-web-webpages-razor-configuration-hostsection-cannot-be-cast-to-web

웹개발을 하면서

[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\MyName\AppData\Local\Temp\Temporary ASP.NET Files\root\63e7ff36\a1cb775d\assembly\dl3\8f568c18\9b7ddacf_d04dcf01\System.Web.WebPages.Razor.dll'.

이런 에러를 만났다.

아...누군가 팀프로젝트에서 이상하게 커밋을 하는 바람에....

삽질...

원인은 web.config

일일이 

runtime / assemblyBinding / dependentAssembly /assemblyIdentity 에 의존성있는거 수정하면서 에러잡음