public async Task <IActionResult> Create(CompetencePrerequisCreateViewModel viewModel)
        {
            ViewData["erreur"] = "";

            if (AlreadyExists(viewModel.Competence, viewModel.Prerequis))
            {
                ViewData["erreur"] = "Element déjà existant";
                ModelState.AddModelError("Intitule", "element existant");
            }

            if (ModelState.IsValid)
            {
                var competence = await _context.Competence
                                 .FirstOrDefaultAsync(m => m.Intitule == viewModel.Competence.Intitule);

                var prerequis = await _context.Prerequis
                                .FirstOrDefaultAsync(m => m.Intitule == viewModel.Prerequis.Intitule);

                var CompetencePrerequisAjoute = new CompetencePrerequis
                {
                    Competence = competence,
                    Prerequis  = prerequis
                };

                _context.Add(CompetencePrerequisAjoute);
                await _context.SaveChangesAsync();

                return(RedirectToAction(nameof(Index)));
            }

            //Permet d'afficher de nouveau les noms des compétences et prérequis dans les SelectList en cas d'erreur
            else
            {
                IQueryable <string> CompetenceQuery = from x in _context.Competence
                                                      orderby x.Intitule
                                                      select x.Intitule;
                IQueryable <string> PrerequisQuery = from x in _context.Prerequis
                                                     orderby x.Intitule
                                                     select x.Intitule;


                viewModel.ListeCompetences = new SelectList(await CompetenceQuery.Distinct().ToListAsync());
                viewModel.ListePrerequis   = new SelectList(await PrerequisQuery.Distinct().ToListAsync());
            }
            return(View(viewModel));
        }
        /// <summary>
        /// Création de nouvelles associations compétences -Prérequis
        /// </summary>
        /// <returns></returns>
        public async Task <IActionResult> Create()
        {
            IQueryable <string> CompetenceQuery = from x in _context.Competence
                                                  orderby x.Intitule
                                                  select x.Intitule;
            IQueryable <string> PrerequisQuery = from x in _context.Prerequis
                                                 orderby x.Intitule
                                                 select x.Intitule;

            var viewModel = new CompetencePrerequisCreateViewModel
            {
                ListeCompetences = new SelectList(await CompetenceQuery.Distinct().ToListAsync()),
                ListePrerequis   = new SelectList(await PrerequisQuery.Distinct().ToListAsync()),
            };

            ViewData["erreur"] = "";
            return(View(viewModel));
        }