private void btnSearch_Click(object sender, EventArgs e) { string pid = ""; string state = ""; if (cboProductName.SelectedIndex > 0) { pid = cboProductName.SelectedValue.ToString(); } if (cboState.SelectedIndex > 0) { state = cboState.Text; } try { WorkOrderService service = new WorkOrderService(); woList = service.SearchWOList(pid, state); string FromDate = periodSearchControl.dtFrom; string ToDate = periodSearchControl.dtTo; List <WorkOrderVO> WorkOrderList = (from wo in woList where Convert.ToDateTime(FromDate) <= Convert.ToDateTime(wo.wo_date) && Convert.ToDateTime(wo.wo_date) <= Convert.ToDateTime(ToDate) select wo).ToList(); dgvOrder.DataSource = WorkOrderList; } catch (Exception err) { MessageBox.Show(err.Message); } }