Group và Sum số lượng trên xtraReport Devexpress

Question

lbl_sumsoluong.DataBindings.Add("Text", DataSource, "slxuat");
            lbl_sumsoluong.Summary = new DevExpress.XtraReports.UI.XRSummary(DevExpress.XtraReports.UI.SummaryRunning.Report, DevExpress.XtraReports.UI.SummaryFunc.Sum, "{0:#,##0.0000}");

* Group Report

GroupHeader1.GroupFields.Add(new GroupField("CategoryID", XRColumnSortOrder.Descending));