By default, ASP.NET MVC loads both the Razor and Web Forms View Engines. This can cause performance issues. Because ASP.NET will look for Web Forms views first, and switch to look for Razor views if Web Forms views cannot be found.
This can be resolved easily by adding the following 2 lines to the Application_Start method in Global.asax.cs.
ViewEngines.Engines.Clear(); ViewEngines.Engines.Add(new RazorViewEngine());