public void get_bill_data()
    {
        string    bill_no = Session["order_bill_no"].ToString();
        DataTable dt      = Select_Logic.select_data_order_selling(bill_no);

        if (dt.Rows.Count > 0)
        {
            ReportDocument   data = new ReportDocument();
            DataSet1_order_s s    = new DataSet1_order_s();
            data.Load(Server.MapPath("crystal_order.rpt")); //crystal report will be loaded in report document
            data.SetDataSource(dt);                         //all data will be filled in report from data table
            CrystalReportViewer1.ReportSource = data;       //assign data in crystal report
        }
    }