private void comboBoxPO_SelectedIndexChanged(object sender, EventArgs e) { if (comboBoxPO.SelectedIndex != -1 && comboBoxPO.SelectedIndex != 0) { POId = Convert.ToInt32(comboBoxPO.SelectedValue.ToString()); retrieve.ShowPOLines(dataGridViewPOLines, PoLineIdGv, ProductIdGv, ProductNameGv, LineNo, ProductPriceGv, ProductQuantityGv, ProductTotalPrice, Convert.ToInt32(comboBoxPO.SelectedValue.ToString()), UnitGv); labelGrandTotalValue.Text = (retrieve.GetPoGrossTotal(Convert.ToInt32(comboBoxPO.SelectedValue.ToString()))).ToString(); } }