จะเอาข้อมูลใน gridview ไปโชว์ใน txtBox รันผ่าน แต่มันไม่โชว์ข้อมูล ไม่รู้ผิดตรงไหน ช่วยดูให้ทีคะ

 void BindData()
        {
            String keyword = this.txtbox_poNo.Text;
            SqlConnection myConn = new SqlConnection();
            int rowcount = 0;
            myConn = new SqlConnection(ConfigurationManager.ConnectionStrings["dbInvoice"].ConnectionString);
            String Sql = "SELECT ORDER_PRODUCT.order_product_id, ORDER_PRODUCT.CUSTOMER_PO_po_id, ORDER_PRODUCT.line_no, STOCK_PRODUCT.product_fullname, ORDER_PRODUCT.PRICELIST_price_id, ORDER_PRODUCT.qty, ORDER_PRODUCT.balance_qty, ORDER_PRODUCT.request_date, ORDER_PRODUCT.committed_date, ORDER_PRODUCT.last_update, EMPLOYEE.emp_name FROM ORDER_PRODUCT INNER JOIN EMPLOYEE ON ORDER_PRODUCT.emp_id = EMPLOYEE.emp_id INNER JOIN STOCK_PRODUCT ON ORDER_PRODUCT.product_id = STOCK_PRODUCT.stock_product_id WHERE ORDER_PRODUCT.CUSTOMER_PO_po_id = '" + keyword + "'";
            myConn.Open();

            SqlDataAdapter da = new SqlDataAdapter(Sql, myConn);
            DataSet ds = new DataSet();
            da.Fill(ds, "ORDER_PRODUCT");
            rowcount = ds.Tables[0].Rows.Count;
            if (rowcount > 0)
            {
                OrderTable.DataSource = ds;
                OrderTable.DataBind();
                OrderTable.Visible = true;
                myConn.Close();
            }
            else
            {
                lblLine.Visible = true;
                lblLine.Text = "This PO Number doesn't have any Line (Products)";
                OrderTable.Visible = false;
            }

        }

        protected void BtnEdit_Click(object sender, EventArgs e)
        {
            int check_count = 0;
            String keyID = "";
            String productid = "";
            String priceid = "";
            CheckBox chkbox = new CheckBox();
            DbProviderFactory factory = DbProviderFactories.GetFactory("System.Data.SqlClient"); 
            IDbConnection con = factory.CreateConnection();
            con.ConnectionString = ConfigurationManager.ConnectionStrings["dbInvoice"].ToString();
            IDbCommand com = factory.CreateCommand(); 
            com.Connection = con;
            con.Open();
            foreach (GridViewRow grdRow in OrderTable.Rows)
            {
                chkbox = (CheckBox)Convert.ChangeType(((CheckBox)grdRow.FindControl("checkdelorder")), typeof(CheckBox));
                if (chkbox.Checked)
                {
                    keyID = (String)OrderTable.DataKeys[grdRow.RowIndex].Value.ToString();
                    Session["update_order_id"] = keyID;
                    check_count++;
                    chkbox.Checked = false;
                }
            }
            if (check_count == 1)
            {
                com.CommandText = "SELECT CUSTOMER_PO_po_id,product_id,PRICELIST_price_id,line_no,qty, balance_qty,request_date,committed_date FROM ORDER_PRODUCT WHERE order_product_id = '" + keyID + "'";

                using (IDataReader reader = com.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        productid = reader.GetString(1).ToString(); // อยู่คนละตาราง เลยแยกไป คิวรี แยกต่างหาก อะคะ
                        priceid = reader.GetString(2).ToString(); // อยู่คนละตาราง เลยแยกไป คิวรี แยกต่างหาก อะคะ 
                        this.txtbox_qty.Text = reader.GetInt32(5).ToString(); // จะให้โชว์ข้อมูลใน txtbox_qty คะ

                    }
                    reader.Close();
                    con.Close();
                }

                com.CommandText = "SELECT product_name FROM STOCK_PRODUCT WHERE stock_product_id = '" + productid + "'";

                using (IDataReader reader = com.ExecuteReader())
                {
                    while (reader.Read())
                    {

                        this.txtbox_productName.Text = reader.GetString(0); // จะให้โชว์ข้อมูลใน txtbox_productName คะ

                    }
                    reader.Close();
                    con.Close();
                }

                com.CommandText = "SELECT commercial_price FROM PRICELIST WHERE price_id = '" + priceid + "'";

                using (IDataReader reader = com.ExecuteReader())
                {
                    while (reader.Read())
                    {

                        this.txtbox_price.Text = reader.GetString(0); // จะให้โชว์ข้อมูลใน txtbox_price คะ

                    }
                    reader.Close();
                    con.Close();
                }

                com.CommandText = "SELECT description FROM STOCK_PRODUCT WHERE stock_product_id = '" + productid + "'";

                using (IDataReader reader = com.ExecuteReader())
                {
                    while (reader.Read())
                    {

                        this.txtbox_descritption.Text = reader.GetString(0); // จะให้โชว์ข้อมูลใน txtbox_descritption คะ

                    }
                    reader.Close();
                    con.Close();
                }

            }
        }