在 MVC 3 中回發到控制器操作後，ViewModel 集合屬性失去了值

我有我的視圖模型：

public class POReceiptViewModel
{
   public virtual int PONumber { get; set; }
   public virtual string VendorCode { get; set; }

   public virtual IList<POReceiptItemViewModel> POReceiptItems { get; set; }

   public POReceiptViewModel()        
   {
       POReceiptItems = new List<POReceiptItemViewModel>();
   }
}

public class POReceiptItemViewModel
{
   public virtual string ItemCode { get; set; }
   public virtual string ItemDesription { get; set; }
   public virtual decimal OrderedQuantity { get; set; }
   public virtual decimal ReceivedQuantity { get; set; }
   public virtual DateTime ReceivedDate { get; set; }

   public POReceiptItemViewModel()
   {
       ReceivedDate = DateTime.Now;
   }
}

然後我的控制器有兩個動作，一個 get 和一個 post：

public ActionResult CreatePOReceipt(int poNumber)
{
   PurchaseOrder po = PurchasingService.GetPurchaseOrder(poNumber);
   POReceiptViewModel poReceiptViewModel = ModelBuilder.POToPOReceiptViewModel(po);
   return View("CreatePOReceipt", poReceiptViewModel);
}

[HttpPost]
public ActionResult CreatePOReceipt(POReceiptViewModel poReceiptViewModel)
{
   // Here the problem goes. The items in the poReceiptViewModel.POReceiptItems has lost. the count became zero.
   return View("Index");
}

在我的視圖中，我可以正確顯示模型，並且通過使用 @Html.HiddenFor<> 我可以根據需要保留視圖模型數據。但不在 List<> 導航屬性上。

@model POReceiptViewModel

@using (Html.BeginForm())
{   
   <fieldset>
       <legend>Purchase Order</legend>
       <label>For PO # :</label>
       @Html.HiddenFor(m => m.PONumber)    
       @Html.DisplayTextFor(m => m.PONumber)
       <label>Vendor Code :</label>
       @Html.HiddenFor(m => m.VendorCode)  
       @Html.DisplayTextFor(m => m.VendorCode)
   </fieldset>

   <fieldset>
       <legend>Received Items</legend>

       <table class="tbl" id="tbl">
          <thead>
          <tr>
          <th>Item Code</th><th>Item Description</th><th>OrderedQuantity</th><th>Received Quantity</th><th>Received Date</th>
          </tr>
          </thead>
          <tbody>
          @Html.HiddenFor(m => m.POReceiptItems) // I'm not really sure if this is valid
          @if (Model.POReceiptItems.Count > 0)
           {
               foreach (var item in Model.POReceiptItems)
               {       
                   <tr>
                       <td>@Html.DisplayTextFor(i => item.ItemCode)</td>@Html.HiddenFor(i => item.ItemCode)    
                       <td>@Html.DisplayTextFor(i => item.ItemDesription)</td>@Html.HiddenFor(i => item.ItemDesription)    
                       <td>@Html.DisplayTextFor(i => item.OrderedQuantity)</td>@Html.HiddenFor(i => item.OrderedQuantity)  
                       <td>@Html.TextBoxFor(i => item.ReceivedQuantity)</td>
                       <td>@Html.TextBoxFor(i => item.ReceivedDate)</td>
                   </tr>
               }
           }
          </tbody>
       </table>
   </fieldset>
   <input type="submit" name="Received" value="Received" />
}

問題： 送出表單時，POReceiptItems 失去。盡可能我不想使用 TempData

$$ “POReceiptItems” $$= Model.POReceiptItems 但即使我使用它，輸入 ReceivedQuantity 和 ReceivedDate 的值也不會保存到 TempData 中。 提前致謝！

嘗試

@for (int i = 0; i < Model.POReceiptItems.Count(); i++)
{ 
<tr>
 <td>@Html.DisplayTextFor(m => m.POReceiptItems[i].ItemCode)</td>@Html.HiddenFor(m => m.POReceiptItems[i].ItemCode)    
 <td>@Html.DisplayTextFor(m => m.POReceiptItems[i].ItemDesription)</td>@Html.HiddenFor(m => m.POReceiptItems.ItemDesription)                                                               <td>@Html.DisplayTextFor(m => m.POReceiptItems[i].OrderedQuantity)</td>@Html.HiddenFor(m => m.POReceiptItems[i].OrderedQuantity)  
 <td>@Html.TextBoxFor(m => m.POReceiptItems[i].ReceivedQuantity)</td>
 <td>@Html.TextBoxFor(m => m.POReceiptItems[i].ReceivedDate)</td>
</tr>
}

另請閱讀此部落格文章以了解模型綁定到列表的工作原理

引用自：https://stackoverflow.com/questions/9646656