Use the SortOrder property value to sort data by the column's values or determine which sort order is currently applied to the column.
Single-Column Sorting (Default) The grid allows data sorting by a single column only, if the DataGridView.SortMode property is set to Single. In this case, when a column's SortOrder is changed, the grid discards the previously applied sorting by another column and sets that column's SortOrder property to None.
Multi-Column Sorting The grid supports multi-column sorting, if the DataGridView.SortMode property is set to Multiple. When a column's SortOrder is changed, the grid does not clear previously applied sorting and uses the new sort order as an additional condition to sort data. To specify the sorting sequence applied to columns, use the GridColumn.SortIndex of these columns.