MVC DropDownList SelectedValue 未正确显示

我尝试搜索，但没有找到任何可以解决我的问题的内容。我在 Razor 视图上有一个 DropDownList，它不会显示我在 SelectList 中标记为“选定”的项目。以下是填充列表的控制器代码：

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>

我浏览了它，即使在视图中它也具有正确的 SelectedValue，但是 DDL 始终显示列表中的第一项，无论选择的值如何。任何人都可以指出我做错了什么让 DDL 默认为 SelectValue 吗？

最后一个论点SelectList构造函数（您希望能够在其中传递选定值 id）将被忽略，因为 DropDownListFor 帮助器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。

所以这是一个丑陋的方法：

Model:

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" },
            }, 
            "ID", 
            "Name"
        );
        ViewBag.Statuses = statuses;

        var model = new MyModel();
        model.StatusID = 3; // preselect the element with ID=3 in the list
        return View(model);
    }
}

View:

@model MyModel
...    
@Html.DropDownListFor(model => model.StatusID, (SelectList)ViewBag.Statuses)

这是正确的方法，使用真实视图模型：

Model

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,
        // 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" },
            }, 
            "ID", 
            "Name"
        );
        var model = new MyModel();
        model.Statuses = statuses;
        model.StatusID = 3; // preselect the element with ID=3 in the list
        return View(model);
    }
}

View:

@model MyModel
...    
@Html.DropDownListFor(model => model.StatusID, Model.Statuses)