Question

只需要另一双眼睛。错误是：

The ViewData item that has the key 'BrandId' is of type 'System.Int32'
but must be of type IEnumerable<SelectListItem>.

HTML

@Html.DropDownListFor(x => x.BrandId, Model.BrandForDropDown, "- Brand -")

控制器

model.BrandForDropDown = Repository.GetBrandsForDropDown();

    public SelectList GetBrandsForDropDown()
    {
        if (Membership.GetUser() != null)
        {
            return new SelectList((from store in DataContext.Stores
                             join userstore in DataContext.UserStores on store.StoreId equals userstore.StoreId
                             join brand in DataContext.Brands on store.BrandID equals brand.BrandID
                             where userstore.UserId == userId
                             select new SelectListItem
                             {
                                 Value = brand.BrandID.ToString(),
                                 Text = brand.BrandName
                             }).OrderBy(x => x.Text));
        }

        return new SelectList(new List<Brand>());
    }

模型

public int BrandId { get; set; }
public SelectList BrandForDropDown { get; set; }
..others omitted

我也在模型和视图等中尝试了List<SelectListItem>，同样的错误

Answer 1

您的代码有一个问题。创建选择列表时，需要指定dataValueField和dataTextField。因此，您必须在服务器方法中或在视图中使用它时执行此操作。

这是你在方法中这样做的方法

select new SelectListItem
                      {
                        Value = brand.BrandID.ToString(),
                        Text = brand.BrandName
                      }).OrderBy(x => x.Text),"Value","Text");

另一种选择是简单地将属性类型更改为List<SelectListItem>并更新您的方法以返回该类型。

public int BrandId { get; set; }
public List<SelectListItem> BrandForDropDown { get; set; }

确保在if条件失败时返回相同的类型

public List<SelectListItem>GetBrandsForDropDown()
{
  if(Membership.GetUser() != null)
  {
    // your existing code
                 select new SelectListItem
                 {
                       Value = brand.BrandID.ToString(),
                       Text = brand.BrandName
                 }).OrderBy(x => x.Text));
  } 
  return new List<SelectListItem();
}

这应该有效

Answer 2

请关注我的技巧。

<强>控制器

ViewBag.BrandForDropDown = Repository.GetBrandsForDropDown();

<强> HTML

@Html.DropDownListFor(x => x.BrandId, ViewBag.BrandForDropDown as   
List<SelectListItem>, "- Brand -")

谢谢。

MVC DropDownListFor问题w / key

2 个答案: