从DropDown中选择选项，并在另一个TextField ASP .NET MVC中自动设置值

public class HomeController : Controller
{
    public ActionResult Index()
    {
        // 获取DropDown的选项列表，这里使用硬编码的方式示例
        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" }
        };

        // 将选项列表传递给视图
        ViewBag.Options = options;

        return View();
    }

    [HttpPost]
    public ActionResult Index(string selectedOption)
    {
        // 根据选择的DropDown选项的值，进行相应的处理
        // 这里简单地将选项的值设置为TextField的值
        ViewBag.SelectedOption = selectedOption;

        return View();
    }
}

@model YourModel

@using (Html.BeginForm())
{
    @Html.DropDownListFor(model => model.SelectedOption, (IEnumerable<SelectListItem>)ViewBag.Options, "请选择一个选项")
    @Html.TextBoxFor(model => model.SelectedOption)

    <input type="submit" value="提交" />
}

$(function () {
    $('#SelectedOption').change(function () {
        var selectedValue = $(this).val();
        $('#SelectedOption').val(selectedValue);
    });
});