protected void Page_Load(object sender, EventArgs e) { //fetch total amount if (!IsPostBack) { txt_total_amount.Text = Select_Logic.select_total_amount_in_order_selling(Session["order_bill_no"].ToString()).Rows[0][0].ToString(); } if (Session["bill_no"] != "") { DataTable dt = Select_Logic.fill_remaining_amoung_order(Session["bill_no"].ToString()); txt_total_amount.Text = dt.Rows[0]["remaininig_amount"].ToString(); } }