public ActionResult Index(Product product)
 {
     if (product.Name != "P1")
     {
         ModelState.AddModelError("Name", "الاسم");
     }
     if (!ModelState.IsValid)
     {
         return View(product);
     }
   
     return RedirectToAction("Index");
 }
        public ActionResult Index()
        {
            //var categories = new List<SelectListItem> {
            //    new SelectListItem { Text = "A 1", Value = "P1",Disabled=true,Group=new SelectListGroup { Name="B"}},
            //    new SelectListItem { Text = "A 2", Value = "P10",Selected=true,Group=new SelectListGroup { Name="A"} },
            //    new SelectListItem { Text = "A 3", Value = "P12",Group=new SelectListGroup { Name="A"} },
            //    new SelectListItem { Text = "A 4", Value = "P" ,Group=new SelectListGroup { Name="B"}}
            //};

            //ViewBag.Categories = categories;
            Product product = new Product();
            product.Type = Models.Type.Special;
            return View(product);
        }