private List <PurchaseOrder> GetPOList()
        {
            PurchaseOrderDAL dal = new PurchaseOrderDAL();
            var pos = dal.SearchPO(txtPurchaseId.Text,
                                   Utility.GetSelectedText(ddlPurchaseStatus),
                                   Utility.GetSelectedText(ddlOrdMan),
                                   Utility.GetSelectedText(ddlMachMan),
                                   Utility.GetSelectedText(ddlPurchaseMan),
                                   Utility.GetSelectedText(ddlApplyPurchaseMan),
                                   Utility.GetSelectedText(ddlMachTableMan),
                                   Utility.GetSelectedText(ddlApproveMan),
                                   !string.IsNullOrEmpty(txtBeginDate.Text) ? DateTime.Parse(txtBeginDate.Text) : DateTime.MinValue,
                                   !string.IsNullOrEmpty(txtEndDate.Text) ? DateTime.Parse(txtEndDate.Text) : DateTime.MaxValue);

            return(pos.ToList());
        }