public class CustomControllerFactory : IControllerFactory

{

    public IController CreateController(System.Web.Routing.RequestContext requestContext, string controllerName)

    {

        if (string.IsNullOrEmpty(controllerName))

            throw new ArgumentNullException("Controller name can't be empty");

        String controllerType = String.Concat("MyMvcApplication.CustomController.", controllerName);

        IController controller = Activator.CreateInstance(Type.GetType(controllerType)) as IController;

        return controller;

    }

    public void ReleaseController(IController controller)

    {

        IDisposable disposableController = controller as IDisposable;

        if (disposableController != null)

            disposableController.Dispose();

    }

}

protected void Application_Start()

{

    RegisterRoutes(RouteTable.Routes);

    ControllerBuilder.Current.SetControllerFactory(typeof(CustomControllerFactory));

}