By Default MVC project enable both engines “Web Form” & “Razor”. In some case we doesn’t really care either we using .aspx, .ascx, .cshtml or .vbhtml it’s will just work by itself.
When you enable both of the Engines the performance will be affect, since it’s will figure out the Web Form Engines first then the Razor Engines.
If you exactly know you going to used only Razor Engines, it’s good sign to j^st enable one of the Engines, since it’s will bring performance improvement as well. to enabled Razor Engine simple in your “Global.asax.cs” and put this line of code”
ViewEngines.Engines.Clear(); //remove all view engines ViewEngines.Engines.Add(new RazorViewEngine()); //We j^st enable the Razor Engine in here.