DropDownListFor使用ViewData进行绑定的示例

特别注意，经实践：

此方法的ViewBag的名称必须和new SelectList（）中的最后一个参数，即下拉框的默认值的名称必须相同，如：

ViewBag.Title = WebConst.UnSelect.Union(new SelectList(WebConst.Dictionary.Where(p => p.Category == "Title").OrderBy(p => p.Sort), "Value", "Display", item.Title));

ViewBag.Title的Title必须和

new SelectList(WebConst.Dictionary.Where(p => p.Category == "Title").OrderBy(p => p.Sort), "Value", "Display", item.Title)

中的item.Title 的Title名字相同，也必须和前台中的

@Html.DropDownListFor(p => p.Title, ViewBag.Title as SelectList, new { @class = "selOp" })的p.Title相同，

否则可能会出现错误，需要特别注意。

另外，如果需要用js向select添加第一项option，如请选择等项，可以使用：

$("selectid").prepend("<option value=''>请选择</option>");

public readonly static IList<SelectListItem> UnSelect = new List<SelectListItem>
  {
   new SelectListItem{Text="请选择",Value=""},
  };

        public readonly static IList<SelectListItem> YesNo = new List<SelectListItem>
  {
   new SelectListItem { Text ="否" , Value = "false"},
   new SelectListItem { Text ="是" , Value = "true"},
  };

ViewBag.PurchaseLimited = WebConst.UnSelect.Union(new SelectList(WebConst.YesNo, "Value", "Text", item.PurchaseLimited));

ViewBag.AcceptPromotionInfo = WebConst.UnSelect.Union(new SelectList(WebConst.YesNo, "Value", "Text", item.AcceptPromotionInfo));

ViewBag.Title = WebConst.UnSelect.Union(new SelectList(WebConst.Dictionary.Where(p => p.Category == "Title").OrderBy(p => p.Sort), "Value", "Display", item.Title));

ViewBag.AgeRange = WebConst.UnSelect.Union(new SelectList(WebConst.Dictionary.Where(p => p.Category == "AgeRange").OrderBy(p => p.Sort), "Value", "Display", item.AgeRange));

//前台使用

<li>
        <label class="required" for="Title">称谓</label>
        <div class="selectArea selectArea2 mln5">
         <span class="selectedItem">选择</span>
         @Html.DropDownListFor(p => p.Title, ViewBag.Title as SelectList, new { @class = "selOp" })
         <em></em>
        </div>
       </li>
       <li>
        <label>婚否</label>
        <div class="selectArea selectArea2 mln5">
         <span class="selectedItem">选择</span>
         @Html.DropDownListFor(p => p.MaritalStatus, ViewBag.MaritalStatus as SelectList, new { @class = "selOp" })
         <em></em>
        </div>
       </li>