ASP MVC重定向而不更改URL(路由)

public ActionResult Index()
{
    TempData["message"] = "Hello World!";
    return RedirectToAction("RedirectedAction");
}

public ActionResult RedirectedAction()
{
    string message = TempData["message"] as string;
    ViewBag.Message = message;
    return View();
}

<h1>@ViewBag.Message</h1>