5

当它回发时，我收到以下错误：

具有键“ClosingDateDay”的 ViewData 项的类型为“System.Int32”，但必须为“IEnumerable”类型。有任何想法吗？

这是我的控制器：

CompetitionEditViewModel viewModel = new CompetitionEditViewModel
{
    ClosingDate = competition.CloseDate,
    Description = competition.Description,
    DescriptionHeading = competition.DescriptionHeading,
    ImageAssetId = competition.ImageAssetId,
    IsActive = competition.IsActive,
    MainHeading = competition.MainHeading,
    TermsAndConditions = competition.TermsAndConditions,
    UrlSlug = competition.UrlSlug
};

viewModel.ClosingDateMonthOptions = new List<SelectListItem>();
for (int i = 1; i <= 12; i++)
{
    string monthName = new DateTime(2000, i, 1).ToString("MMMM");
    ((List<SelectListItem>)viewModel.ClosingDateMonthOptions).Add(new SelectListItem { Text = monthName, Value = i.ToString() });
}

viewModel.ClosingDateDayOptions = new List<SelectListItem>();
for (int i = 1; i <= 31; i++)
{
    ((List<SelectListItem>)viewModel.ClosingDateDayOptions).Add(new SelectListItem { Text = i.ToString().PadLeft(2, '0'), Value = i.ToString() });
}

viewModel.ClosingDateYearOptions = new List<SelectListItem>();
for (int i = DateTime.Now.Year; i <= DateTime.Now.Year + 3; i++)
{
    ((List<SelectListItem>)viewModel.ClosingDateYearOptions).Add(new SelectListItem { Text = i.ToString(), Value = i.ToString() });
}

这是我的观点：

@Html.Uber().LabelFor(x => x.ClosingDateDay, new { @class = "access" })
@Html.DropDownListFor(x => x.ClosingDateDay, Model.ClosingDateDayOptions, Model.ClosingDateDay)

@Html.Uber().LabelFor(x => x.ClosingDateMonth, new { @class = "access" })
@Html.DropDownListFor(x => x.ClosingDateMonth, Model.ClosingDateMonthOptions, Model.ClosingDateMonth)

@Html.Uber().LabelFor(x => x.ClosingDateYear, new { @class = "access" })
@Html.DropDownListFor(x => x.ClosingDateYear, Model.ClosingDateYearOptions, Model.ClosingDateYear)
4

2 回答 2

9

在构造 SelectListItem 类时，将Selected要最初选择的项目的属性设置为 true。

于 2012-06-21T19:43:42.270 回答
1

我在我的一个项目中所做的并且有点用处的是，开发了另外两个
DropDownListFor接受的重载selectedValue。 

namespace MyMvcApplication.Helpers
{
    public static class ExtensionMethods
    {
        public static MvcHtmlString DropDownListFor<TModel, TProperty>
                             (this HtmlHelper<TModel> helper,
                              Expression<Func<TModel, TProperty>> expression,
                              string selectedValue,
                              IEnumerable<SelectListItem> selectList,
                              string optionLabel,
                              object htmlAttributes)
        {
            if (string.IsNullOrEmpty(selectedValue))
                selectedValue = string.Empty;
            if (selectList != null)
            {
                foreach (SelectListItem sli in selectList)
                {
                    if (sli.Value.ToLower().Trim() == selectedValue.ToLower().Trim())
                    {
                        sli.Selected = true;
                        break;
                    }
                }
            }
            else 
            { 
                selectList = new List<SelectListItem>() 
                                  { new SelectListItem() 
                                          { Text = "", Value = "", Selected = true }
                                  };
            }
            return helper.DropDownListFor(expression, selectList, optionLabel, htmlAttributes);
        }


        public static MvcHtmlString DropDownListFor<TModel, TProperty>
                             (this HtmlHelper<TModel> helper,
                              Expression<Func<TModel, TProperty>> expression,
                              string selectedValue,
                              IEnumerable<SelectListItem> selectList,
                              string optionLabel,
                              IDictionary<string, object> htmlAttributes)
        {
            if (string.IsNullOrEmpty(selectedValue))
                selectedValue = string.Empty;
            if (selectList != null)
            {
                foreach (SelectListItem sli in selectList)
                {
                    if (sli.Value.ToLower().Trim() == selectedValue.ToLower().Trim())
                    {
                        sli.Selected = true;
                        break;
                    }
                }
            }
            else 
            { 
                selectList = new List<SelectListItem>() 
                                  { new SelectListItem() 
                                          { Text = "", Value = "", Selected = true } 
                                  };
            }
            return helper.DropDownListFor(expression, selectList, optionLabel, htmlAttributes);
        }

    }
}

所以在视图中，我可以将一个字符串作为 selectedValue 传递给DropDownListFor，例如：

@using MyMvcApplication.Helpers

@Html.DropDownListFor(model => model.MyData,
                               "Default Value for DropDownList", //Or Model.MySelectedValue
                               Model.MySelectList, null, mull)
于 2012-06-22T17:01:41.880 回答