session and cookies in mvc5

Question

I have lost data in session/cookies when I call the action of controller second time.what is the reason of this problem?

 

my code is given below...

[HttpPost]
public ActionResult AddCart(long productId,double Qty,decimal price)
{
decimal TotAmount = 0;
long userId = 0,OrderId=0;
string status = "incart";
DataTable dt = new DataTable();
try
{
//var session = HttpContext.Session;
//if (session["orderid"] != null)
//{
// OrderId =Convert.ToInt64(session["orderid"].ToString());
// TotAmount = Convert.ToDecimal(session["orderAmt"]);
//}
HttpCookie myCookie = Request.Cookies["order"];
if (myCookie != null)
{
OrderId =Convert.ToInt64(myCookie.Values["orderid"]);
//Response.Write("
" + myCookie.Name + "

" + myCookie.Value);

}
TotAmount = TotAmount + price;
SqlCommand cmd = new SqlCommand("OrderSave", con);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("@PKOderId", OrderId);
cmd.Parameters.AddWithValue("@PKUserId", userId);
cmd.Parameters.AddWithValue("@TotAmount", TotAmount);
cmd.Parameters.AddWithValue("@Status", status);
cmd.Parameters.AddWithValue("@FKRowStatusId", 1);
cmd.Parameters.AddWithValue("@TimeStamp", DateTime.Now);
con.Open();
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dt);
con.Close();
if(dt.Rows.Count>0)
{
OrderId = Convert.ToInt64(dt.Rows[0]["PKOrderId"].ToString());
userId= Convert.ToInt64(dt.Rows[0]["PKUserId"].ToString());
TotAmount= Convert.ToDecimal(dt.Rows[0]["TotalAmount"].ToString());
long cartid = 0;
SqlCommand cmdcart = new SqlCommand("AddCart", con);
cmdcart.CommandType = CommandType.StoredProcedure;
cmdcart.Parameters.AddWithValue("@PKCartId", cartid);
cmdcart.Parameters.AddWithValue("@PKOrderId", OrderId);
cmdcart.Parameters.AddWithValue("@PKProductId", productId);
cmdcart.Parameters.AddWithValue("@Quantity", Qty);
cmdcart.Parameters.AddWithValue("@FKRowStatusId", 1);
cmdcart.Parameters.AddWithValue("@TimeStamp", DateTime.Now);
con.Open();
cartid = Convert.ToInt64(cmdcart.ExecuteScalar());
con.Close();
if(cartid>0)
{
//session.Add("orderid",OrderId.ToString());
//session.Add("orderAmt",TotAmount.ToString());
HttpCookie order = new HttpCookie("order");
order.Values["orderid"] = OrderId.ToString();
// Add the cookie.
Response.Cookies.Add(order);
status = "success";
}
bool sess= Session["orderid"]!=null?true:false;
}
}
catch(Exception ex)
{
Console.WriteLine(ex);
status = "failed";
}
return Json(status,JsonRequestBehavior.AllowGet);
}

The boolean sess gets value of session...but in next postback the session/cookie returns null.