public ActionResult AddExamen(int examenId)
        {
            repositorio.AddExamen(new UsuarioExamen
            {
                ExamenId  = examenId,
                UsuarioId = auth.GetLoggedUser().Id
            });

            TempData["SuccessMessage"] = "Usted se ha registrado correctamente al examen";

            return(RedirectToAction("Index", "Home"));
        }