MVC设置下拉列表的选定项目的问题

Question

在我的控制器中，我按如下方式设置了SelectedYear字段;

[Authorize(Roles = "Administrator, AdminAccounts")]
public ActionResult BankHoliday(int? id)
{
    BankHolidayViewModel BankHolidayViewModel = new BankHolidayViewModel();

    int year = DateTime.Now.Year;
    if (id.HasValue)
       year = id.GetValueOrDefault();

    BankHolidayViewModel.SelectedYear = year;
    BankHolidayViewModel.GetYearData(year);
    return View(BankHolidayViewModel);
}

每当我单步执行代码时，返回语句中的SelectedYear值始终是正确的。在下面的Year DropDownList中，这是在DropDownList中设置所选项的Value字段;

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/AdminAccounts.master" Inherits="System.Web.Mvc.ViewPage<SHP.WebUI.Models.BankHolidayViewModel>" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
    BankHoliday
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="AdminAccountsContent" runat="server">
        <h3>Bank Holiday Administration</h3>
        <p>Select the year: <%: Html.DropDownListFor(model => model.SelectedYear, Model.YearList)%></p>
       <script language="javascript" type="text/javascript">
            $(function () {
                $("#SelectedYear").change(function () {
                    var year = $("#SelectedYear").val();
                    $("#wholepage").load("/AdminAccounts/BankHoliday/" + year);
                });
            });

*编辑：添加信息*

YearList定义如下;

public class BankHolidayViewModel
{
    public IList<BankHolidayExtended> BankHolidays { get; set; }
    public IList<BankHolidayYear> Years { get; set; }
    public int SelectedYear = DateTime.Now.Year;
    public IEnumerable<SelectListItem> YearList
    {
        get
        {
            return this.Years.Select(item => new SelectListItem
            {
                Text = item.Year.ToString(),
                Value = item.Year.ToString()
            });
        }
    }

* END EDIT *

出于某种原因，在呈现视图时，下拉列表中没有选定的项目。我该如何解决这个问题？

Answer 1

您的“继承”需要继承您的ViewModel。

Inherits="System.Web.Mvc.ViewPage<ViewModels.BankHolidayViewModel>"

创建YearList时，还需要设置所选值。像

这样的东西

 YearList = new SelectList(GetYears(), "year", "year", SelectedYear);

修改的 在您的视图中，您可以设置所选值：

<%= Html.DropDownListFor(x => x.SelectedYear, new SelectList(Model.YearList, "Value", "Text", Model.SelectedYear))%>

或者你可以在我最初设置年份列表时执行此操作。 GetYears（）将返回列表的年份。

public SelectList YearList { get; private set; }
public class BankHolidayViewModel(int year)
{
    YearList = new SelectList(GetYears(), "Value", "Text", year);

然后返回视图

return View(new BankHolidayViewModel(year));

Answer 2

我真的不想将我的对象更改为SelectList，尽管我确信这会有效。 相反，我通过改变吸气剂得到了答案;

public IEnumerable<SelectListItem> YearList
{
    get
    {
        return this.Years.Select(item => new SelectListItem
        {
            Text = item.Year.ToString(),
            Value = item.Year.ToString(),
            Selected = item.Year == this.SelectedYear
        });
    }
}