public ActionResult Ajouter(Client client) { using (var dal = new ClientDal()) { if (dal.Existe(client.Nom, client.Prenom)) { ViewBag.MessageErreur = "Ce client existe déjà"; ModelState.AddModelError("Client", "Ce client existe déjà"); } if (!ModelState.IsValid) { return(View(client)); } dal.Add(client.Nom, client.Prenom, client.Email); return(RedirectToAction("Index")); } }