ASP.NET @Html.TextBoxFor :如何在刷新页面时不丢失用户输入的值？

public ActionResult Index()
{
    // 从Session中获取保存的值
    string userInput = Session["UserInput"] as string;
    
    // 将值传递给视图
    ViewBag.UserInput = userInput;
    
    return View();
}

[HttpPost]
public ActionResult Index(string userInput)
{
    // 将用户输入的值保存到Session中
    Session["UserInput"] = userInput;
    
    return RedirectToAction("Index");
}

@using (Html.BeginForm())
{
    @Html.TextBoxFor(model => model.UserInput, new { @value = ViewBag.UserInput })
    <input type="submit" value="提交" />
}