public void AddCategories(int[] categories, int productId, bool isEditing) { if (isEditing) { var oldCategories = _categoryRepository.GetProductCategories(productId).ToList(); _categoryRepository.DeleteProductCategories(oldCategories); _categoryRepository.SaveChanges(); } var newCategories = new List <ProductCategory>(); foreach (var item in categories) { newCategories.Add(new ProductCategory { CategoryId = item, ProductId = productId }); } _categoryRepository.AddProductCategories(newCategories); _categoryRepository.SaveChanges(); }