ViewBag.Message not working?

Question

im using asp.net mvc my viewbag message not  working can someone help me. 

 

else

{

var order = new Order

{

ClientId = model.ClientId,

StateId = model.StateId,

CityId = model.CityId,

TownId = model.TownId,

Postcode = model.Postcode,

Address = model.Address,

DatePosted = DateTime.Now,

DeliveryDate = Convert.ToDateTime(model.DeliveryDate),

Quantity = model.Quantity,

Status = "Lined-up",

DateDelivered = null,

Notes = model.Notes ?? ""

};

_orderService.Add(order);

ViewBag.Message = "Your order successfully inserted";

return RedirectToAction("add");

}

 

 My script

@if (ViewBag.Message != null)

{

<script type="text/javascript">

window.onload = function () {

alert("@ViewBag.Message");

};

</script>

}