我尝试搜索，没有找到任何解决问题的东西。我在Razor视图中有一个DropDownList，它不会显示在SelectList中标记为Selected的项目。这是填写列表的控制器代码：
var statuses = new SelectList(db.OrderStatuses,"ID","Name",order.Status.ID.ToString()); ViewBag.Statuses = statuses; return View(vm);
这是查看代码：
<div class="display-label"> Order Status</div> <div class="editor-field"> @Html.DropDownListFor(model => model.StatusID,(SelectList)ViewBag.Statuses) @Html.ValidationMessageFor(model => model.StatusID) </div>
我走过它，即使在视图中它具有正确的SelectedValue，但是DDL始终显示列表中的第一个项目，而不管选择的值如何。任何人都可以指出我做错了什么来让DDL默认为SelectValue？
解决方法
SelectList构造函数(希望能够传递所选值id)的最后一个参数被忽略，因为DropDownListFor Helper使用您作为第一个参数传递的lambda表达式，并使用特定属性的值。
所以这是丑陋的方法：
模型：
public class MyModel
{
public int StatusID { get; set; }
}
控制器：
public class HomeController : Controller
{
public ActionResult Index()
{
// TODO: obvIoUsly this comes from your DB,// but I hate showing code on SO that people are
// not able to compile and play with because it has
// gazzilion of external dependencies
var statuses = new SelectList(
new[]
{
new { ID = 1,Name = "status 1" },new { ID = 2,Name = "status 2" },new { ID = 3,Name = "status 3" },new { ID = 4,Name = "status 4" },},"Name"
);
ViewBag.Statuses = statuses;
var model = new MyModel();
model.StatusID = 3; // preselect the element with ID=3 in the list
return View(model);
}
}
视图：
@model MyModel ... @Html.DropDownListFor(model => model.StatusID,(SelectList)ViewBag.Statuses)
这是正确的方式，使用真实的视图模型：
模型
public class MyModel
{
public int StatusID { get; set; }
public IEnumerable<SelectListItem> Statuses { get; set; }
}
控制器：
public class HomeController : Controller
{
public ActionResult Index()
{
// TODO: obvIoUsly this comes from your DB,"Name"
);
var model = new MyModel();
model.Statuses = statuses;
model.StatusID = 3; // preselect the element with ID=3 in the list
return View(model);
}
}
视图：
@model MyModel ... @Html.DropDownListFor(model => model.StatusID,Model.Statuses)
