protected virtual void DoRefreshData()
        {
            int columnIndex = fPivot.GetColumnIndex(fColumnValues);
            int rowIndex    = fPivot.GetRowIndex(fRowValues);

            if (columnIndex < 0 || rowIndex < 0)
            {
                drillDownView.DataSource = null;
            }
            else
            {
                drillDownView.DataSource = fPivot.CreateDrillDownDataSource(columnIndex, rowIndex);
            }
            drillDownView.PopulateColumns();
        }