Theme-able View Engine in ASP.NET MVC 4/5

Global.asax.cs

        private void InitializeViewEngine()
        {
            HostingEnvironment.RegisterVirtualPathProvider(new DynamicAssetVirtualPathProvider());
            
            ViewEngines.Engines.Clear();
            ViewEngines.Engines.Add(new ThemableViewEngine
            {
                Theme = ctx => DependencyResolver.Current.GetService<ISiteContext>().Theme.ThemeName
            });
        }

ThemeableViewEngine.cs

    public class ThemableViewEngine : ThemeableRazorViewEngine
    {
        public ThemableViewEngine()
        {
            // ~/themes/default/views/projects/list.cshtml
            ViewLocationFormats = new[] {
                "~/Themes/{2}/Views/{1}/{0}.cshtml",
                "~/Themes/{2}/Views/Shared/{0}.cshtml",
                "~/Views/{1}/{0}.cshtml",
                "~/Views/Shared/{0}.cshtml"
            };

            // Master pages must be inside a "shared" directory
            // ~/themes/default/views/shared/_layout.cshtml
            MasterLocationFormats = new[] { 
                "~/Themes/{2}/Views/Shared/{0}.cshtml",
                "~/Views/Shared/{0}.cshtml"
            };

            // ~/themes/default/views/shared/_menu.cshtml
            PartialViewLocationFormats = new[] {
                "~/Themes/{2}/Views/{1}/{0}.cshtml",
                "~/Themes/{2}/Views/Shared/{0}.cshtml",

                "~/Views/{1}/{0}.cshtml",
                "~/Views/Shared/{0}.cshtml"
            };

            ViewStartFileExtensions = new[] { "cshtml" };
        }
    }

What is this? Do you have any article or implementation for this?