When data is grouped by a specific column, the View's rows are combined into groups. By default, each group contains rows which have the same value in the field (column) for which grouping has been applied. Use the GroupInterval property to change the logic used to decide which rows should be grouped together. For instance, for a column that displays date/time information, you can set its GroupInterval property to DevExpress.XtraGrid.ColumnGroupInterval.DateYear. In this case, when grouping is applied against this column, the data rows will be combined into groups according to the year part of their values. See the DevExpress.XtraGrid.ColumnGroupInterval topic, for information on the other options.
The order in which group rows are arranged is specified by the SortOrder and SortMode properties.
To provide custom grouping logic when data is grouped by a specific column, set the column's SortMode property to DevExpress.XtraGrid.ColumnSortMode.Custom, and handle the GridView.CustomColumnGroup event.
See Working with Groups in Code for an overview of group modes.
Group rows can be painted in the standard manner or using the Office2003 paint style. To specify how group rows should be painted, use the GridOptionsView.GroupDrawMode property.
An end-user can change the group interval for date-time columns at runtime via a context menu if the GridOptionsMenu.ShowDateTimeGroupIntervalItems option is enabled.