ASP.NET MVC - Html.DropDownList - 未通过ViewData.Model设置的值

public ActionResult Index()
{
    // 创建一个下拉列表的数据源
    List<SelectListItem> items = new List<SelectListItem>();
    items.Add(new SelectListItem { Text = "Item 1", Value = "1" });
    items.Add(new SelectListItem { Text = "Item 2", Value = "2" });
    items.Add(new SelectListItem { Text = "Item 3", Value = "3" });

    // 将下拉列表的数据源添加到ViewBag中
    ViewBag.Items = items;

    return View();
}

@Html.DropDownList("Items", ViewBag.Items as List<SelectListItem>)