Я следовал инструкции в этом посте post, но когда я пытаюсь добавить продукт, я получаю эту ошибку:
Server Error in '/' Application.
--------------------------------------------------------------------------------
Value cannot be null.
Parameter name: source
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.ArgumentNullException: Value cannot be null.
Parameter name: source
Source Error:
Line 63:
Код контроллера:
public ActionResult Create()
{
ViewBag.PossibleCategory = context.Categories;
return View();
}
//
// POST: /Product/Create
[HttpPost]
public ActionResult Create(Product product)
{
if (ModelState.IsValid)
{
context.Products.Add(product);
context.SaveChanges();
return RedirectToAction("Index");
}
ViewBag.PossibleCategory = context.Categories;
return View(product);
}
И код вида:
@Html.DropDownListFor(model => model.CategoryId, ((IEnumerable)ViewBag.PossibleCategories).Select(option => new SelectListItem {
Text = (option == null ? "None" : option.Name),
Value = option.Id.ToString(),
Selected = (Model != null) && (option.Id == Model.CategoryId)
}), "Choose...")
@Html.ValidationMessageFor(model => model.CategoryId)