The name ViewBag does not exist in the current context

Question

[HttpPost]

public ActionResult Index(tblUser ob)

{

if (ob.emp_no != null && ob.pass != null && ob.pass != "")

{

if (ModelState.IsValid)

{

billMangeSys_Entities billentity = new billMangeSys_Entities();

var user = billentity.tblUsers.Single(x => x.emp_no == ob.emp_no && x.pass == ob.pass);

if (user != null)

{

// return View(user);

return RedirectToAction("dashboard");

}

}

}

else {

ViewBag.Message = string.Format("Hello {0}.\\nCurrent Date and Time: {1}", name, DateTime.Now.ToString());

}

return View();

}