public IActionResult Add()
        {
            //LİSTELERİ OLUŞTUR, FOREACH İLE İÇLERİNİ DOLDUR
            List <SelectListItem> SelectCategory = new List <SelectListItem> {
                new SelectListItem(text: "Kategori Seçiniz", value: "")
            };
            List <SelectListItem> SelectCompany = new List <SelectListItem> {
                new SelectListItem(text: "Firma Seçiniz", value: "")
            };

            foreach (var item in ICategoryServices.CategoryListItem())
            {
                SelectCategory.Add(new SelectListItem {
                    Text = item.CategoryName, Value = item.ID.ToString()
                });
            }


            foreach (var item2 in ICompanyServices.CompanyListItem())
            {
                SelectCompany.Add(new SelectListItem {
                    Text = item2.CompanyName, Value = item2.ID.ToString()
                });
            }

            //LİSTELER TAMAM, MODELİ OLUŞTURUP İLGİLİ ALANLARA SETLE VİEW'A YOLLA

            ProductAddModel productAddModel = new ProductAddModel
            {
                CategorySelectList = SelectCategory,
                CompanySelecList   = SelectCompany
            };

            return(View(productAddModel));
        }