DropDownList与MVC4中可能嵌套的DropDownList

Question

我有一组用户可以选择的问题,其中一些问题有一个可供选择的辅助选项列表.我的目标是有一个下拉列表,如果你选择其中一个选项,其中包含其SecondaryChoiceList中的项目,那么第二个列表将出现在初始下拉列表下方,所有这些都将被强类型并在提交时绑定到模型.

我可以通过以下方式获得初始列表:

@Html.DropDownListFor( x => x.SelectedChoiceId, new SelectList(Model.Choices, "Id", "Name"))

但是,这与辅助列表没有挂钩,我完全迷失了如何将该辅助列表与我提交表单时返回的模型联系起来.

这是我的视图模型:

public class ExampleViewModel
{
    public List<Choice> ChoiceList { get; set; }
    public int SelectedChoiceId { get; set; }
    public int SelectedAffiliateId { get; set; }
}

以下是选择的样子:

public class Choice
{
    public int Id { get; set; }
    public string Name { get; set; }
    public IEnumerable<SecondaryChoice> SecondaryChoiceList { get; set; }

    public Choice()
    {
        SecondaryChoiceList = new List<SecondaryChoice>();
    }
}

这是我的SecondaryChoice对象:

public class EligibleAffiliate
{
    public int Id { get; set; }
    public int EligibilityChoiceId { get; set; }
    public string Name { get; set; }
}

如果有任何我可以清理的事情让我知道.

我的乌龟,我提前感谢你

@Html.DropDownListFor( x => x.SelectedChoiceId, new SelectList(Model.Choices, "Id", "Name"))

Answer 1

我试图让它尽可能简单.

因此,下面给出了一个样本模型:

namespace StackOverflow.Models
{
    public class Choice
    {
        public int Id { get; set; }
        public string Name { get; set; }

        public Choice()
        {
            Id = 0;
        }

        public Choice(int id, string name)
        {
            Id = id;
            Name = name;
        }
    }
}


namespace StackOverflow.Models
{
    public class ExampleViewModel
    {
        public List<Choice> PrimaryChoiceList { get; set; }
        public List<Choice> SecondaryChoiceList { get; set; }
        public int SelectedChoiceId { get; set; }
        public int SelectedAffiliateId { get; set; }

        public ExampleViewModel()
        {
            SelectedChoiceId = 0;
            SelectedAffiliateId = 0;

            PrimaryChoiceList = new List<Choice>()
            {
                new Choice(1, "How are you?"),
                new Choice(2, "How is the weahter?"),
                new Choice(3, "What have you been doing so far?"),
                new Choice(4, "What's up man?"),
                new Choice(5, "Any news?"),
                new Choice(5, "Bla bla bla")
            };

            SecondaryChoiceList = new List<Choice>()
            {
                new Choice(1, "How are you dear?"),
                new Choice(2, "How is the weahter?"),
                new Choice(3, "What have you been doing so far dear?"),
                new Choice(4, "What's up man?"),
                new Choice(5, "Any romantic news?")
            };
        }
    }
}

样品控制器:

namespace StackOverFlow.Controllers
{
    public class SOController : Controller
    {
        public static ExampleViewModel evm = new ExampleViewModel();

        public ActionResult Index()
        {
            return View(evm);
        }

        public ActionResult SetSelection(int id)
        {
            evm.SelectedChoiceId = id;

            if (evm.PrimaryChoiceList.Count() > 0)
            {
                Choice selection = evm.PrimaryChoiceList.ElementAt(id-1);
                Choice affiliate = (Choice)evm.SecondaryChoiceList.FirstOrDefault(x => x.Name == selection.Name);
                if (affiliate != null)
                {
                    return Content("show");
                }
                else
                {
                    return Content("hide");
                }
            }
            else
            {
                return Content("hide");
            }
        }
    }
}

和网页:

@using StackOverflow2.Models;
@model ExampleViewModel

<script src="@Url.Content("~/Scripts/jquery-1.7.1.min.js")" type="text/javascript"></script>

@{
    ViewBag.Title = "Stackoverflow Sample";
}

<h2>Index</h2>

<script type="text/javascript">

    // Get the selection and make Ajax Request to the controller, action: SetSelection,
    // which in turn may decide whetger you must show or hide the control
    function updateSeconadryQuestion(id) {
        var xmlhttp;
        if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
            xmlhttp = new XMLHttpRequest();
        }
        else {// code for IE6, IE5
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        xmlhttp.onreadystatechange = function () {
            if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                if (xmlhttp.responseText == 'show')
                    $('#SecondaryQuestionDropBoxId').show();
                else
                    $('#SecondaryQuestionDropBoxId').hide();
            }
        }
        xmlhttp.open("GET", "/SO/SetSelection?id=" + id, true);
        xmlhttp.send();
    }

</script>

@Html.DropDownListFor(x => x.SelectedChoiceId, new SelectList(Model.PrimaryChoiceList, "Id", "Name", "Value"), new { id = "PrimaryQuestionDropBoxId", onchange = "updateSeconadryQuestion(value);" })

<div id="SeconadryQuestionDivId">
@Html.DropDownListFor(x => x.SelectedAffiliateId, new SelectList(Model.SecondaryChoiceList, "Id", "Name"), new { id = "SecondaryQuestionDropBoxId" })
</div>