Linq lambda group by aggregate by multiple columns

Example of grouping input DataTable by string column and getting aggregate MAX for second bool column:

     var sTables = (bindSrcColumns.DataSource as DataTable).Rows.Cast<DataRow>())
                        .GroupBy(r =>   ColumnsHelper.GetTablePart(r[EDITORCOLUMN_FIELDNAME].ToString()))
                        .Select(g => new Tuple<string, bool>(g.Key, g.Max(m => m[EDITORCOLUMN_ISSELECTED] as bool? ?? false)))
                        .OrderBy(s=>s.Item1)
                        .ToList();