AllowCellMerge

how to

            mainview.OptionsView.AllowCellMerge = true;
            mainview.CellMerge += CellMerge;
            
                    private void CellMerge(object sender, CellMergeEventArgs e)
        {
            GridView mainview = (this.ViewList["GridMain"] as C_GridControl).MainView as GridView;

            if (e.Column.FieldName == "CUSTOMERID")
            {
                var d1 = mainview.GetDataRow(e.RowHandle1);
                var d2 = mainview.GetDataRow(e.RowHandle2);
                e.Merge = d1["CUSTOMERID"].ToString().Equals(d2["CUSTOMERID"].ToString());
            }
            else
            {
                e.Merge = false;
            }

            e.Handled = true;
        }