将模型数据从视图传递到控制器

Question

我正在尝试通过 HttpPost 将模型数据从视图（以及视图中的 PartialView）传回控制器。 （改编自Pass SelectedValue of DropDownList in Html.BeginForm() in ASP.NEt MVC 3）

为什么？我想显示一个资产列表，每个资产都有一个 DropDownList 和选项数量。提交表单后从 DropDownList 中读取所选项目。

我的 2 个（简化）模型：

public class Booking
{
    public int BookingID { get; set; }
    public int StoreID { get; set; }
    ...
    public IEnumerable<AssetShort> Assets { get; set; }
}

和

public class AssetShort
{
    public int AssetID { get; set; }
    ....
    public int SelectedAction { get; set; }
    public IEnumerable<SelectListItem> ActionList { get; set; }
}

在我的 Booking Controller > Create 中构建列表：

public ActionResult Booking(int id)
    {
     // get myBag which contains a List<Asset>
     //  booking corresponds to 'id'

        var myAssets = new List<AssetShort>();
        foreach (var a in myBag.Assets)
        {
            var b = new AssetShort();
            b.AssetID = a.ID;
            b.SelectedAction = 0;
            b.ActionList = new[]
                { 
            new SelectListItem { Selected = true, Value = "0", Text = "Select..."},
            new SelectListItem { Selected = false, Value = "1", Text = "Add"},
            new SelectListItem { Selected = false, Value = "2", Text = "Remove"},
            new SelectListItem { Selected = false, Value = "3", Text = "Relocate"},
            new SelectListItem { Selected = false, Value = "4", Text = "Upgrade"},
            new SelectListItem { Selected = false, Value = "5", Text = "Downgrade"}
                };
            myAssets.Add(b);
        };

        var model = new BookingRequirementsViewModel
            {
                BookingID = booking.ID,
                StoreID = booking.StoreID,
                Assets = myAssets.ToList(),
            };
        return View(model);

我的观点：

@model uatlab.ViewModels.BookingRequirementsViewModel
@{
    ViewBag.Title = "Booking step 2";
}
<h4>Your booking ref. @Model.BookingID</h4>
@using (Html.BeginForm("Booking2", "Booking", FormMethod.Post))
{
<fieldset>
  @Html.AntiForgeryToken()
  @Html.HiddenFor(model => model.StoreID)

  @Html.Partial("_Assets", Model.StoreAssets)

  <input type="submit" value="Cancel" class="btn btn-default" />
  <input type="submit" value="Next" class="btn btn-default" />
</fieldset>
}

部分视图包括

@foreach (var item in Model)
{
    <tr>
        <td>@item.Name</td>
        <td>@item.Number</td>
        <td>@Html.DropDownListFor(modelItem=>item.SelectedAction, item.ActionList)</td>
    </tr>
}

因此，所有这些在浏览器中都可以正常工作，我可以为列出的每个资产选择下拉列表，但是当我提交时，唯一回发的值是 StoreID，因为它在“HiddenFor”中。

booking2 控制器有一个参数的模型：

public ActionResult Booking2(BookingRequirementsViewModel model)
{
    //loop through model.Assets and display SelectedActions
}

让我澄清一下问题所在 - 在 Booking2 控制器中，在调试模式下查看时模型为空，并且我收到错误“对象引用未设置为对象的实例”。

请教如何将模型从视图传回控制器？

问候 克雷格

Answer 1

您需要为AssetShort 创建一个EditorTemplate。我还建议将ActionList 移动到BookingRequirementsViewModel，这样您就不会为每个AssetShort 重新生成一个新的SelectList

您发布的模型没有意义。您的控制器有var model = new BookingRequirementsViewModel { ..., Assets = myAssets.ToList() };，但在视图中您指的是@Html.Partial("_Assets", Model.StoreAssets)？这是2个不同的属性。我会假设StoreAssets 是IEnumerable<AssetShort>

/Views/Shared/EditorTemplates/AssetShort.cshtml

@model AssetShort
<tr>
  <td>@Html.DispayFor(m => m.Name)</td>
  ....
  <td>
    @Html.DropDownListFor(m => m.SelectedAction, (IEnumerable<SelectListItem>)ViewData["actionList"], "--Please select--")
    @Html.ValidationMessageFor(m => m.SelectedAction)
  </td>
</tr>

在主视图中

@model uatlab.ViewModels.BookingRequirementsViewModel
....
@using (Html.BeginForm()) // Not sure why you post to a method with a different name
{
  ....
  @Html.HiddenFor(m => m.StoreID)
  @Html.EditorFor(m => m.StoreAssets, new { actionList = Model.ActionList })
  ....
}

在控制器中

public ActionResult Booking(int id)
{
  ....
  var model = new BookingRequirementsViewModel
  {
    BookingID = booking.ID,
    StoreID = booking.StoreID,
    Assets = myBag.Assets.Select(a => new AssetShort()
    {
      AssetID = a.ID,
      SelectedAction = a.SelectedAction, // assign this if you want a selected option, otherwise the "--Please select--" option will be selected
      ....
    })
  };
  ConfigureViewModel(model); // Assign select list
  return View(model);
}

还有一个单独的方法来生成SelectList，因为如果您返回视图，则需要在 GET 方法中调用它，并在 POST 方法中再次调用它。注意使用DropDownListFor()的重载生成选项标签（空值）如上，设置Selected属性没有意义（SelectedAction的值决定选择什么，不是这个）

private ConfigureViewModel(BookingRequirementsViewModel model)
{
  model.ActionList = new[]
  {
    new SelectListItem { Value = "1", Text = "Add"},
    ....
    new SelectListItem { Value = "5", Text = "Downgrade"}
  };
}

和 POST

public ActionResult Booking(BookingRequirementsViewModel model)
{
  if (!ModelState.IsValid)
  {
    ConfigureViewModel(model); // Re-assign select list
    return View(model);
  }
  // save and redirect
}

我建议还使用 [Required] 属性使 SelectedAction 可以为空，以便您获得客户端和服务器端验证

public class AssetShort
{
  public int AssetID { get; set; }
  ....
  [Required]
  public int? SelectedAction { get; set; }
}