如何在asp.net mvc中选择一个选择列表项？

public class MyViewModel
{
    public int SelectedItem { get; set; }
    public List<SelectListItem> Items { get; set; }
}

public ActionResult Index()
{
    var viewModel = new MyViewModel
    {
        Items = new List<SelectListItem>
        {
            new SelectListItem { Value = "1", Text = "选项1" },
            new SelectListItem { Value = "2", Text = "选项2" },
            new SelectListItem { Value = "3", Text = "选项3" }
        }
    };

    return View(viewModel);
}

@model MyViewModel

@Html.DropDownListFor(m => m.SelectedItem, Model.Items, "请选择一个选项", new { @class = "form-control" })

[HttpPost]
public ActionResult Index(MyViewModel viewModel)
{
    int selectedItem = viewModel.SelectedItem;

    // 处理选择的值

    return RedirectToAction("Index");
}