Microsoft recent security update has resulted in compilation error. After spending some time came across this link. This is a known issue.
Error: Could not load file or assembly 'System.Web.Mvc, Version=126.96.36.199, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
Cause of Error: Microsoft recent security update
Solution: Install Nuget Package Microsoft.AspNet.Mvc for all the project referencing System.Web.Mvc dll
Example: Install-Package Microsoft.AspNet.Mvc