private void FindButton_Click(object sender, RoutedEventArgs e) { gridControl1.ShowLoadingPanel = true; gridControl1.ItemsSource = null; QLThuebaoDomainContext dstb = new QLThuebaoDomainContext(); InvokeOperation<System.Nullable<int>> p = dstb.Excute_p_tklydocat(dngaybd.DateTime, dngaykt.DateTime); p.Completed += new EventHandler(Completed); }