Mvc如果ModelState无效，如何保持dropdownlist的选定值

public ActionResult YourAction()
{
    // 获取dropdownlist的选定值
    string selectedValue = "option2"; // 假设选定值为"option2"

    // 将选定值存储在ViewBag中
    ViewBag.SelectedValue = selectedValue;

    // 或者将选定值存储在ViewModel中
    var model = new YourViewModel();
    model.SelectedValue = selectedValue;

    return View(model);
}

@model YourViewModel

@* 使用@Html.DropDownListFor生成dropdownlist，并设置选中项 *@
@Html.DropDownListFor(model => model.SelectedValue, YourSelectList, "Please select")

@* 或者使用@Html.DropDownList生成dropdownlist，并设置选中项 *@
@Html.DropDownList("SelectedValue", YourSelectList, "Please select")