将模型数据从视图传递到控制器

Question

我想通过HttpPost将模型数据从视图（和视图内的PartialView）传递回控制器。 （改编自Pass SelectedValue of DropDownList in Html.BeginForm() in ASP.NEt MVC 3）

为什么？我想显示每个具有DropDownList和多个选项的资产列表。提交表单以从DropDownList中读取所选项目。

我2（简体）型号：

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; } 
} 

在我的预订控制器>创建我生成列表：

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); 

笔者认为：

@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> 
} 

局部视图包括

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

所以，这一切工作正常，在浏览器中，我可以列出的每个资产选择的下拉列表中，但是当我提出调回唯一的价值是STOREID因为它是在一个“ HiddenFor”。

的booking2控制器有一个参数型号：

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

让我说清楚的问题是 - 在Booking2控制器的型号为NULL在调试模式下查看时，我得到错误“对象引用未设置为对象的实例。“

任何想法，请如何从视图回传模型到控制器？

问候 克雷格

Answer 1

你需要创建一个AssetShortEditorTemplate。我还建议把ActionList到BookingRequirementsViewModel所以你不能再生每个AssetShort

您发布不决策意识的车型新SelectList。您的控制器有var model = new BookingRequirementsViewModel { ..., Assets = myAssets.ToList() };，但在您看来您指的是@Html.Partial("_Assets", Model.StoreAssets)？这两个不同的属性。我会认为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

@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

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); 
} 

而且一个单独的方法来生成SelectList因此如果您返回视图，则需要在GET方法中调用它，并在POST方法中再次调用它。注意使用的DropDownListFor()过载以生成选项标签（空值）如上，并且没有点设置Selected属性（的SelectedAction值确定什么被选择时，没有此）

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 
} 

我建议也正在与[Required]属性SelectedAction为空的，所以你得到的客户端和服务器端验证

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