public void refreshPurchaseInvoices()
        {
            var saleDS         = new DataSet();
            var itemsDataTable = new DataTable("PurchaseOrders");

            itemsDataTable.Columns.Add("Pruchase Date");
            itemsDataTable.Columns.Add("Pruchase Amount");
            itemsDataTable.Columns.Add("Amount Paid");
            itemsDataTable.Columns.Add("Pruchase Status");
            itemsDataTable.Columns.Add("User Name");

            using (var db = new Model.posdbEntities())
            {
                var query = (from v in db.purchasesorders
                             orderby v.PurchaseDate descending
                             select v
                             ).ToList();


                foreach (var item in query)
                {
                    itemsDataTable.Rows.Add(item.PurchaseDate.Value.ToShortDateString(), item.PurchaseAmount, item.AmountPaid, item.PurchaseStatus, item.UserName);
                }

                saleDS.Tables.Add(itemsDataTable);
                PurchaseInvoices.DataSource = saleDS;
                PurchaseInvoices.DataMember = "PurchaseOrders";
                PurchaseInvoices.Refresh();
            }
        }