Question

在asp.net mvc 4 Web应用程序中，我使用viewmodel将我的数据加载到页面，编辑部分数据并更新相关模型。

目前我遇到了@Html.DropDownList，虽然下拉列表显示正常，但根据您选择的内容，它不会更改/更新。

知道为什么会发生这种情况以及我做错了什么？

以下是我的代码：

控制器：

public ActionResult RequestDetails(int id)
{
  var details = from s in SystemDB.Events.ToList()
                where s.BookingId == id
                orderby s.EventId descending
                select s;
  List<RequestDetailsViewModel> result = new List<RequestDetailsViewModel>();
  foreach (var item in details)
  {
    RequestDetailsViewModel model = new RequestDetailsViewModel();
    model.Event.EventId = item.EventId;
    model.Event.EventLeader = item.EventLeader;
    model.Event.EventStartDateTime = item.EventStartDateTime;
    model.Event.EventEndDateTime = item.EventEndDateTime;
    model.Event.Room.RoomNumber = item.Room.RoomNumber;
    model.Event.EventTotalCost = item.EventTotalCost;
    model.Event.Booking.BookingId = item.BookingId;              
    result.Add(model);              
  }
  Booking booking = SystemDB.Bookings.Find(id);
  var statuscodes = from s in SystemDB.StatusCodes.ToList()
                    where s.StatusCodeId != 1
                    select s;
  ViewBag.StatusCodeList = new SelectList(statuscodes, "StatusCodeId", "StatusCodeName", booking.StatusCodeId);
  return View(result);
}

[HttpPost]
[ActionName("RequestDetails")]
public ActionResult PostRequestDetails(int id)
{
  var details = from s in SystemDB.Events.ToList()
                where s.BookingId == id
                orderby s.EventId descending
                select s;
  List<RequestDetailsViewModel> result = new List<RequestDetailsViewModel>();
  foreach (var item in details)
  {
    RequestDetailsViewModel model = new RequestDetailsViewModel();
    model.Event.EventId = item.EventId;
    model.Event.EventLeader = item.EventLeader;
    model.Event.EventStartDateTime = item.EventStartDateTime;
    model.Event.EventEndDateTime = item.EventEndDateTime;
    model.Event.Room.RoomNumber = item.Room.RoomNumber;
    model.Event.EventTotalCost = item.EventTotalCost;
    model.Event.Booking.BookingId = item.BookingId;             
    result.Add(model);
 }
 Booking booking = SystemDB.Bookings.Find(id);
 var statuscodes = from s in SystemDB.StatusCodes.ToList()
                   where s.StatusCodeId != 1
                   select s;
 ViewBag.StatusCodeList = new SelectList(statuscodes, "StatusCodeId", "StatusCodeName", booking.StatusCodeId);
  if (ModelState.IsValid)
  {
    SystemDB.Entry(booking).State = EntityState.Modified;
    SystemDB.SaveChanges();
    return RedirectToAction("RequestList", "Admin");
  }                
  return View(result);
}

Viewmodel：

public class RequestDetailsViewModel
{
  public RequestDetailsViewModel()
  {
    this.Event = new Event();
    this.CateringItem = new CateringItem();
    this.Item = new Item();
    this.Event.Room = new Room();
    this.Event.Booking = new Booking();
    this.Event.Booking.StatusCode = new StatusCode();
  }
  public Event Event { get; set; }
  public CateringItem CateringItem { get; set; }
  public Item Item { get; set; }  
}

查看：

@model IEnumerable<CateringBookingSystem.ViewModels.RequestDetailsViewModel>

@Html.ActionLink("Manage Requests", "RequestList")/<b>Event List</b>

@using (Html.BeginForm("RequestDetails", "Admin", FormMethod.Post))
{ 
  <span><b>Booking for: </b>@ViewBag.Date</span>
  <span style="padding-left:20px;"><b>Total Cost: </b>£@ViewBag.BookingTotalCost</span>
  <span style="padding-left:20px;"><b>Requester: </b><a href="mailto:'@ViewBag.RequesterEmail'?Subject=Catering%20enquiry" target="_top">@ViewBag.Requester</a></span>
  <span style="padding-left:20px;"><b>Status: </b> @Html.DropDownList("StatusCodeList")  </span>

  <table id="listTable" style="width:100%" >
    <tr style="color:white;">
      <th>@Html.DisplayNameFor(model => model.Event.EventLeader)</th>
      <th>@Html.DisplayNameFor(model => model.Event.EventStartDateTime</th>
      <th>@Html.DisplayNameFor(model => model.Event.EventEndDateTime</th>
      <th>@Html.DisplayNameFor(model => model.Event.Room.RoomNumber)</th>
      <th>@Html.DisplayNameFor(model => model.Event.EventTotalCost)</th>        
    </tr>
    @foreach (var item in Model)
    {
      <tr>
        <td>@Html.DisplayFor(modelItem => item.Event.EventLeader)</td>
        <td>@Html.DisplayFor(modelItem => item.Event.EventStartDateTime)</td>
        <td>@Html.DisplayFor(modelItem => item.Event.EventEndDateTime</td>
        <td>@Html.DisplayFor(modelItem => item.Event.Room.RoomNumber)</td>
        <td>£@Html.DisplayFor(modelItem => item.Event.EventTotalCost</td>
      </tr>
    }
  </table>
  <div style="padding-top:50px;">
    <input type="submit" value="submit" />
  </div>
}

<div style="padding-top:20px;">
  <img src="~/Images/arrow-return-180-left.png" style="margin-bottom:-3px;margin-right:-4px;" /> @Html.ActionLink("Back to Requests", "RequestList")
</div>

Answer 1

试试这个

 @Html.DropDownList("StatusCodeList", (SelectList) ViewBag.StatusCodeList, "Select")

Answer 2

您的ViewBag.StatusCodeList已经是SelectList的类型。我没有看到两次创建SelectList的原因，所以不应该只是：

@Html.DropDownList("StatusCodeList", ViewBag.StatusCodeList)

或

@Html.DropDownList("StatusCodeList", ViewBag.StatusCodeList as SelectList)

Answer 3

你GET方法正在向视图返回RequestDetailsViewModel的集合。要正确呈现集合以进行回发，请使用自定义EditorTemplate作为RequestDetailsViewModel类型，并将POST方法更改为

[HttpPost]
public ActionResult RequestDetails(IEnumerable<RequestDetailsViewModel> model)

注意，在大多数情况下，您可以使用for循环在视图中呈现集合，但DropDownListFor()中存在一个错误，阻止控件在{{1}中正确绑定} loop（尽管你绑定了属性的值，但总会选择第一个选项。）

编辑模板

/Views/Shared/EditorTemplates/RequestDetailsViewModel.cshtml

for

在主视图中，您需要将@model RequestDetailsViewModel @Html.HiddenFor(m => m.Event.Booking.EventId) @Html.TextBoxFor(m => m.Event.Booking.EventLeader) .... @Html.DropDownListFor(m => m.Event.Booking.StatusCodeId, (SelectList)ViewData["StatusCodeList"], "-Please select-") ....传递给SelectList参数

中的模板

additionalViewData

GET方法

@model IEnumerable<RequestDetailsViewModel>
@using(Html.BeginForm())
{
  @Html.EditorFor(m => m, new { StatusCodeList = (SelectList)ViewBag.StatusCodeList })
  <input type="submit" />
}

@ Html.DropDownList不选择值

3 个答案: