Question

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'，但必须是'IEnumerable'类型。有什么想法吗？

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() });
}

继承了我的观点：

@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)

Answer 1

构造SelectListItem类时，请为最初选择的项目将Selected属性设置为true。

Answer 2

我在我的一个项目中所做的并且有点有用，就是为了增加2个重载接受DropDownListFor的{{1}}。

selectedValue

所以在Views中，我可以将一个字符串作为selectedValue传递给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); } } }，如：

DropDownListFor

设置Html.DropDownList（）的默认值

2 个答案: