Modificando o Layout/MasterPage via atributo no ASP.NET MVC

gistfile1.cs

//MvcApplication1\Infrastructure\ChangeLayoutAttribute.cs
using System.Web.Mvc;

namespace MvcApplication1.Infrastructure
{
    public class ChangeLayoutAttribute : ActionFilterAttribute, IResultFilter
    {
        public override void OnResultExecuting(ResultExecutingContext filterContext)
        {
            var viewResult = filterContext.Result as ViewResult;
            if (viewResult != null)
            {
                // realiza lógica para escolha do layout caso seja Razor ou masterpage caso seja ASPX
                viewResult.MasterName = "AdminMaster";
            }
        }
    }
}

//MvcApplication1\Controllers\AdminController .cs
namespace MvcApplication1.Controlllers
{
    [ChangeLayout]
    public class AdminController : Controller
    {
        //
        // GET: /Admin/
        //[ChangeLayout]
        public ActionResult Index()
        {
            return View();
        }
    }
}