I did the upgrade according to. http://www.asp.net/mvc/tutorials/mvc-5/how-to-upgrade-an-aspnet-mvc-4-and-web-api-project-to-aspnet-mvc-5-and-web-api-2
I get the er
You need to add assembly redirects:
.... ...
Most likely you have to do this for a few more assemblies like webhosting, etc.