如何使用MVC在选项上创建具有自定义数据属性的DropDownList，并保留验证？

public class DropdownModel
{
    [Required(ErrorMessage = "请选择一个选项")]
    public string SelectedOption { get; set; }

    // 其他属性...
}

public IActionResult Index()
{
    // 从数据库或其他来源获取选项数据
    var options = 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" }
    };

    var model = new DropdownModel();
    ViewBag.Options = options;

    return View(model);
}

@model DropdownModel

@using (Html.BeginForm("Index", "Home", FormMethod.Post))
{
    @Html.DropDownListFor(m => m.SelectedOption, ViewBag.Options as List<SelectListItem>, new { data_customattribute = "customvalue" })
    @Html.ValidationMessageFor(m => m.SelectedOption)
    <input type="submit" value="提交" />
}

[HttpPost]
public IActionResult Index(DropdownModel model)
{
    if (ModelState.IsValid)
    {
        // 执行其他操作...
        return RedirectToAction("Success");
    }

    // 验证失败，重新加载选项数据并返回视图
    var options = 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" }
    };

    ViewBag.Options = options;
    return View(model);
}