How to maintain data between Get and Post Method for same view in ASP.NET MVC?

Question

Currently I am having this sample code

        public ActionResult SampleView()
        {
            TempData["datetime"] = "Tempdata:  " + DateTime.Now.ToString();

            ViewBag.datetime = "ViewBag:   " + DateTime.Now.ToString();

            ViewData["datetime"] = "ViewData:  " + DateTime.Now.ToString();

            return View();

        }

        [HttpPost]
        public ActionResult SampleView(int? x) // 'x' is dummy variable, no use
        {
            string datetime1 = TempData["datetime"].ToString();

            string datetime2 = ViewBag.datetime;

            string datetime3 = ViewData["datetime"].ToString();    

            return RedirectToAction("SampleView");
        }

But none of the above retain the values between GET and POST. Any Solution ?