DropDownList在MVC4中可能嵌套DropDownList

Question

我有一组用户可以选择的问题，其中一些问题有第二个可供选择的选项列表。我的目标是有一个下拉列表，如果您选择其SecondaryChoiceList中有项目的选项之一，那么第二个列表将显示在初始下拉列表下方，并且所有这些都将在提交时被强制键入并绑定到模型。

我可以得到初步名单说出现：

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

但是这并没有钩到次列表，我完全失去了，我怎么会配合该次列表回模型我提交表单时会返回。

这里是我的视图模型：

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

这里是一个选择的样子：

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>(); 
    } 
} 

这里是我的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除让我知道。

我的乌龟，我感谢你提前

___ 
//_\\ _ Thxs! 
/_|_|_('> 
" " 

Answer 1

我试图保持尽可能简单。

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> 

所以，一个样品模型如下