Visual studio: CS0234: The type or namesapece name 'Ajax' does not exist in the namespace etc

Exception:

"CS0234: The type or namespace name 'Ajax' does not exist in the namespace 'System.Web.Mvc' (are you missing an assembly reference?)"

Solution:

To fix, update or uninstall and install, or reinstall Asp.Net MVC using Nuget Package manager.

To reinstall using nuget console, using following command:

update-package –reinstall Microsoft.AspNet.Mvc

For more information, see here.