从剃刀视图中的循环中删除列表

Question

我想在剃刀视图中的循环中使用下拉列表。下拉列表在初始页面加载时正确显示，但模型绑定在帖子上不起作用。在下拉列表中选择的项目在帖子中不可用。 tableColumns属性是空的。任何帮助将非常感激。

型号

public class DataMappingViewModel 
     {   

public string TableName { get; set; } 
     public List<XmlElement> XmlElements { get; set; } 

    } 
    public class XmlElement 
    { 
     public string ElementName { get; set; } 
     public List<SP_GET_DBASE_COLUMNS_Result> tableColumns { get; set; } 
    } 

     public partial class SP_GET_DBASE_COLUMNS_Result 
    { 
     public string TABLE_CATALOG { get; set; } 
     public string TABLE_SCHEMA { get; set; } 
     public string TABLE_NAME { get; set; } 
     public string COLUMN_NAME { get; set; } 
     public Nullable<int> ORDINAL_POSITION { get; set; } 
     public string COLUMN_DEFAULT { get; set; } 
     public string IS_NULLABLE { get; set; } 
     public string DATA_TYPE { get; set; } 
     public Nullable<int> CHARACTER_MAXIMUM_LENGTH { get; set; } 
     public Nullable<int> CHARACTER_OCTET_LENGTH { get; set; } 
     public Nullable<byte> NUMERIC_PRECISION { get; set; } 
     public Nullable<short> NUMERIC_PRECISION_RADIX { get; set; } 
     public Nullable<int> NUMERIC_SCALE { get; set; } 
     public Nullable<short> DATETIME_PRECISION { get; set; } 
     public string CHARACTER_SET_CATALOG { get; set; } 
     public string CHARACTER_SET_SCHEMA { get; set; } 
     public string CHARACTER_SET_NAME { get; set; } 
     public string COLLATION_CATALOG { get; set; } 
     public string COLLATION_SCHEMA { get; set; } 
     public string COLLATION_NAME { get; set; } 
     public string DOMAIN_CATALOG { get; set; } 
     public string DOMAIN_SCHEMA { get; set; } 
     public string DOMAIN_NAME { get; set; } 
    } 

控制器

public ActionResult Index() 
     { 

      List<XmlElement> elements = new List<XmlElement>(); 

      XmlElement element1 = new XmlElement(); 
      element1.ElementName = "element1"; 
      element1.tableColumns = data.GetTableColumns("TABLENAME"); 

      elements.Add(element1); 

      DataMappingViewModel viewitem = new DataMappingViewModel(); 

      viewitem.XmlElements = elements; 
      viewitem.TableName = "TABLENAME"; 


      return View(viewitem); 
     } 


     [HttpPost] 
     public ActionResult MapData(DataMappingViewModel model) 
     { 
      return View("Index",model); 
     } 

查看

@model ExcelImportAPI.Models.DataMappingViewModel 
@using System.Web.Mvc; 
@{ 
    ViewBag.Title = "title"; 
    Layout = "~/Views/Shared/_Layout.cshtml"; 
} 


@using (Html.BeginForm("MapData", "DataMapping", FormMethod.Post)) 
{ 

    <h2>Data Mapping</h2> 

for (var i = 0; i < Model.XmlElements.Count; i++) 
{ 

    @Html.HiddenFor(m => Model.XmlElements[i].ElementName) 
    @Model.XmlElements[i].ElementName 

     <td> 
      @Html.DropDownList("tableColumns", new SelectList(@Model.XmlElements[i].tableColumns, "COLUMN_NAME", "COLUMN_NAME"), "--Select a Value--") 


     </td> 
    } 

    <div class="modal-footer"> 
     <input type="submit" name="btnSaveAndExit" value="Save and Exit" class="btn btn-default"> 
     <input type="submit" name="btnSaveAndContinue" value="Save and Continue" class="btn btn-primary modal-btn"> 
    </div> 

}