c# - 没有具有键 'IEnumerable' 的 'Register.CountryId' 类型的 ViewData 项

Question

代码运行正常，但我没有收到错误:

There is no ViewData item of type 'IEnumerable' that has the key 'Register.CountryId'

可见:

 @using (Html.BeginForm((string)ViewBag.FormAction, "NMPAccount", new { @id = "myForm", @name = "myForm" }))

 @Html.LabelFor(m => m.Register.CountryId)
 @Html.DropDownListFor(m => m.Register.CountryId, Model.Register.CountryList,  
                                                    new { @id = "CountryList" })
 @Html.ValidationMessageFor(m => m.Register.CountryId)

}

在 Controller 中:

[AllowAnonymous]
public ActionResult Register() {
    var registerViewModel = new RegisterViewModel();
    registerViewModel.Initalize();
    return View("Register", registerViewModel);

}

    [AllowAnonymous]
    [HttpPost]
    public ActionResult Register(RegisterViewModel model) {
        if (!ModelState.IsValid) {
            model.Initalize();
            ModelState.AddModelError(string.Empty, "");
            return View("Register", model);

        }

        if (ModelState.IsValid && model.Register != null) {
            if (RegisterViewModel.RegisterNewUser(model.Register))
                return RedirectToAction("RegisterSuccess");
            else
                ModelState.AddModelError("", NMPAccountResource.Failed);

        }

在 ViewModel 中:

public class RegisterViewModel {
        public RegisterViewModel() {
            Register = new RegisterModel();
        }

        public RegisterModel Register { get; set; }

        public void Initalize() {
            var registerUser = new RegisterUser();
            IList<CountryCodes> couList = Utilities.GetCountryList(languageId);
            var countryList = (from data in couList
                               select new CustomItem() {
                                   Id = data.CountryCodesId,
                                   Description = data.CountryName

                               }).ToList();
            if (countryList.Count > 0) {
                countryList[0].Id = null;
            }


            var clist = new SelectList(countryList, "Id", "Description");

            Register.CountryList = clist;
        }

** 注册模型**:

   public string CountryId { get; set; }
   public IEnumerable<SelectListItem> CountryList { get; set; } 

我想从“ View 模型”执行此操作。

我搜索了 StackOverflow，但没有找到解决我问题的答案。

Answer 1

我无法将其添加为评论，但您需要在 Register 操作的 POST 版本中返回一个 View 模型

    [AllowAnonymous]
        [HttpPost]
        public ActionResult Register(RegisterViewModel model) {
            if (!ModelState.IsValid) {
                model.Initalize();
                ModelState.AddModelError(string.Empty, "");
                return View("Register", model);

            }

            if (ModelState.IsValid && model.Register != null) {
                if (RegisterViewModel.RegisterNewUser(model.Register))
                    return RedirectToAction("RegisterSuccess");
                else
                {
                    ModelState.AddModelError("", NMPAccountResource.Failed);
               //there needs to be code here to return the view.
               return View("Register", model); //<--- this is missing
               }

            }
               //there needs to be code here to return the view.
               return View("Register", model); //<--- this is missing

   }

如果条件 !ModelState.IsValid 为 TRUE，您的代码之前可能一直有效。也许您没有通过此检查，下面的代码在运行时失败。