DropdownListFor在HTTP回傳後返回空

Question

應用程序的上下文是維護來自投資顧問的安全訂單。在用戶修改他的訂單的屏幕上出現問題。在這樣的屏幕中，我有下拉列表來指定訂單類型，無論是買入還是賣出，並顯示安全，數量和價格的值。

問題 同時在編輯界面是我親眼目睹，做一個修改後（測試已通過改變購買/賣出但其他人即價格進行不）。如果我執行HTTP Post，則DropDownList的值將返回null。參見截圖：

初始化SelectList型

public static List<SelectListItem> getBuySellList() 
     { 
      List<SelectListItem> buySell = new List<SelectListItem>(); 

      SelectListItem item; 

      item = new SelectListItem(); 
      item.Text = "BUY"; 
      item.Value = "BUY"; 
      buySell.Add(item); 

      item = new SelectListItem(); 
      item.Text = "SELL"; 
      item.Value = "SELL"; 
      buySell.Add(item); 

      return buySell; 
     } 

我的控制器如下：

// GET: OrderFlow/Edit/5 
     public ActionResult Edit(int id) 
     { 
      OrderFlowModel orderFlowModel = db.Find(id); 

      ViewData["ORDERFLOW_NO"] = id; 
      ViewBag.OrderFlowBuySell = Utility.UtilityDBContext.getBuySellList(); 

      return View(orderFlowModel); 
     } 

     [HttpPost] 
     [ValidateAntiForgeryToken] 
     public ActionResult Edit(string OrderFlowNo, string OrderFlowSecurityID, string OrderFlowBuySell, string OrderFlowQuantity, string OrderFlowPrice, string OrderFlowTradingDate, string OrderFlowClientAccount, string OrderFlowParticipant, string OrderFlowBuyStatus) 
     { 
      if (ModelState.IsValid) 
      { 

       OrderFlowModel orderFlowModel = new OrderFlowModel(); 
       orderFlowModel.OrderFlowNo = int.Parse(OrderFlowNo.ToString()); 
       orderFlowModel.EquityID = OrderFlowSecurityID; 
       orderFlowModel.BuySell = OrderFlowBuySell; 
       orderFlowModel.Quantity = int.Parse(OrderFlowQuantity); 
       orderFlowModel.Price = double.Parse(OrderFlowPrice); 

       DateTime dt; 
       if (DateTime.TryParseExact(OrderFlowTradingDate, formats, System.Globalization.CultureInfo.InvariantCulture, DateTimeStyles.None, out dt)) 
       { 
        orderFlowModel.TradingDate = dt; 
       } 
       else orderFlowModel.TradingDate = DateTime.Today; 

       orderFlowModel.ClientAccountID = OrderFlowClientAccount; 
       orderFlowModel.ParticipantAccountID = OrderFlowParticipant; 
       orderFlowModel.Status = OrderFlowBuyStatus; 

       try 
       { 
        db.Edit(orderFlowModel); 
        return RedirectToAction("Index"); 
       } 
       catch (Exception er) 
       { 
        TempData["Message"] = er.Message; 
       } 

      } 

      ViewBag.OrderFlowBuySell = Utility.UtilityDBContext.getBuySellList(); 
      return RedirectToAction("Edit", new{id=OrderFlowNo}); 
     } 

的OrderFlow型號：

public class OrderFlowModel 
    { 
     [Display(Name = "Order Flow No")] 
     public int OrderFlowNo { get; set; } 

     [Display(Name = "Valid Till")] 
     [DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}")] 
     [DataType(DataType.Date)] 
     public DateTime TradingDate { get; set; } 

     [Display(Name = "Client A/c ID")] 
     public string ClientAccountID { get; set; } 

     [Display(Name = "Participant ID")] 
     public string ParticipantAccountID { get; set; } 

     [Required(ErrorMessage="Security is Required")] 
     [Display(Name = "Security")] 
     public string EquityID { get; set; } 

     [Required(ErrorMessage = "Buy or Sell Needs to specify")] 
     [Display(Name = "BS")] 
     public string BuySell { get; set; } 

     [DefaultSettingValue("0")] 
     [Display(Name = "Quantity")] 
     [DisplayFormat(DataFormatString = "{0:N0}")] 
     public int Quantity { get; set; } 

     [Display(Name = "Price")] 
     [DataType(DataType.Currency)] 
     [DisplayFormat(DataFormatString = "{0:N2}")] 
     public double Price { get; set; } 

     [Display(Name = "Status")] 
     public string Status { get; set; } 

     [Display(Name = "User Entered")] 
     public string UserEntered { get; set; } 

     [Display(Name = "Effective From")] 
     [DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}")] 
     public DateTime EffectiveStart { get; set; } 

     [Display(Name = "Effective Till")] 
     [DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}")] 
     public DateTime EffectiveEnd { get; set; } 
    } 

我在剃刀分配DropdownListFor如下的方式：從瀏覽器

@Html.DropDownListFor(model => model.BuySell, new SelectList(ViewBag.OrderFlowBuySell, "Text", "Value"), new { @id = "OrderFlowBuySell", @class = "form-control" }) 

HTML輸出下拉列表

<select class="form-control" data-val="true" data-val-required="Buy or Sell Needs to specify" id="OrderFlowBuySell" name="BuySell"><option selected="selected" value="BUY">BUY</option> 
<option value="SELL">SELL</option> 
</select> 

Answer 1

需要在你的控制器的方法是BuySell的價值，這是從下面加價的下拉列表中選擇的ID（第一個參數）：

@Html.DropDownListFor(model => model.BuySell, 
     new SelectList(ViewBag.OrderFlowBuySell, "Text", "Value"), 
     new { @id = "OrderFlowBuySell", @class = "form-control" }) 

的OrderFlowBuySell是COLLEC用於綁定下拉列表的選項，在帖子中您通常只關注用戶選擇的選項。

其更改爲這個和值將被張貼：

Edit(string OrderFlowNo, string OrderFlowSecurityID, 
    string OrderFlowBuySell, string OrderFlowQuantity, 
    string OrderFlowPrice, string OrderFlowTradingDate, 
    string OrderFlowClientAccount, string OrderFlowParticipant, 
    string OrderFlowBuyStatus, string BuySell) 

不過，我會強烈建議您使用的ViewModels，這樣你可以speficy一個對象到控制器後。