具有相同选择列表的多个Html.dropdownlist，设置选择的值

Question

我有一个带有多个dropdownlistfor的Add / Edit视图，所有视图都来自同一选择列表。当我尝试填充editinng的视图时，所有dropdownlist的选择与第一个相同。有没有解决的办法？我不想使用多个选择列表，因为它们都具有相同的内容。

大多数下拉列表都是从一个列表创建的，每个项目都有一个下拉列表。这是视图的第一部分，它不是从项目列表创建的。

        <div class="control-group">
            @Html.LabelFor(model => model.FirstRound, new { @class = "control-label" })
            <div class="controls">
                @Html.DropDownListFor(model => Model.FirstRound.Id, Model.Difficulties, new { @class = "span3 combobox"})
                @Html.TextBoxFor(model => Model.FirstRound.Value, new { @class = "input-xlarge span1 sec-val", @readonly = "readonly"})
                @Html.ValidationMessageFor(model => model.FirstRound.Value, null, new { @class = "help-inline" })
            </div>
        </div>

这是我循环项目列表以创建下拉列表的部分。

@{int counter = 0;}
        @foreach (var item in Model.SecondRound)
        {

            <div class="control-group">
                @Html.LabelFor(model => model.SecondRound, new { @class = "control-label" })
                <div class="controls second-round">
                    @Html.DropDownListFor(model => model.SecondRound[counter].Id, Model.Difficulties, new { @class = "span3 combobox", @id = "SecondRound[" + counter + "].Id" })
                    @Html.TextBoxFor(model => Model.SecondRound[counter].Value, new { @class = "input-xlarge span1 sec-val", @readonly = "readonly"})
                    @Html.ValidationMessageFor(model => Model.SecondRound[counter].Value, null, new { @class = "help-inline" })
                </div>
            </div>
            <hr />
            counter = counter + 1;
        }

这是我的ViewModel

public class AddTariffTrampetVM
{
    public string Team { get; set; }
    [HiddenInput(DisplayValue=false)]
    public int NumberOfGymnasts { get; set; }

    [Display(Name="Difficulty")]
    public RoundVM FirstRound { get; set; }
    [Range(0.001d, 100.0d, ErrorMessage="You need to pick a difficulty for the first round!")]
    public decimal FirstTotalValue { get; set; }

    [Display(Name = "Difficulty")]
    public IList<RoundVM> SecondRound { get; set; }
    [Range(0.001d, 100.0d, ErrorMessage = "You need to pick difficulties for the second round!")]
    public decimal SecondTotalValue { get; set; }

    [Display(Name = "Difficulty")]
    public IList<RoundVM> ThirdRound { get; set; }
    [Range(0.001d, 100.0d, ErrorMessage = "You need to pick difficulties for the third round!")]
    public decimal ThirdTotalValue { get; set; }

    public List<SelectListItem> Difficulties { get; set; }

    public AddTariffTrampetVM() : this(6)
    {
    }

    public AddTariffTrampetVM(int numOfGymnast)
    {
        NumberOfGymnasts = numOfGymnast;

        FirstRound = new RoundVM { Id = 0, Value = 0M };
        SecondRound = new List<RoundVM>();
        ThirdRound = new List<RoundVM>();
        for (int i = 0; i < NumberOfGymnasts; i++)
        {
            SecondRound.Add(new RoundVM());
            ThirdRound.Add(new RoundVM());
        }
    }
}

public class RoundVM {
    public int Id { get; set; }
    [Range(0.001d, 100.0d, ErrorMessage="Your need to pick a difficulty!")]
    public decimal Value { get; set; }


    public RoundVM()
    {
        Value = 0M;
    }
}

这是我填写表格的“编辑”操作

    public ActionResult Edit(int id)
    {
        var item = ServiceTariff.GetTariffTrampet(id);
        var model = Mapper.Map<TariffTrampet, AddTariffTrampetVM>(item);
        model.Difficulties = ServiceDifficulty.GetSelectListElementTrampet().ToList();

        return View("Add", model);
    }

希望有人可以帮助我。如果您需要更多代码，请注释。

Answer 1

与其仅提供Model.Difficulties给DropDownListFor助手，不如尝试传递它：

new SelectList(Model.Difficulties, object selectedValue)

或另一个重载，可让您指定值和文本字段：

new SelectList(Model.Difficulties, string dataValueField, string dataTextField, object selectedValue)

使用其中一个作为DropDownListFor辅助程序的第二个参数。SelectList从中创建List<SelectListItem>允许您设置初始选择的值。