Group Modes and Custom Grouping
#Group Modes
By default, when grouping by date/time values, only the date portion of values is taken into account, while the time portion is ignored. Thus, rows that contain matching date portions, but different time portions in a grouping column, are combined into a single group. If grouping columns contain other data types, default grouping logic is used. In this instance, rows are combined into a single group, if they have a matching value in a grouping column.
The Interval Grouping feature allows you to change the default logic, especially for columns that contain date/time values. For example, data rows can be arranged by the month or year part of a date/time value, while text columns can be grouped by the first characters. To specify the required grouping mode, use the column's GridColumn.GroupInterval property.
#Custom Grouping
If the built-in grouping modes don't suit your requirements, you can implement custom logic. To do this, set the ColumnBase.SortMode property to 'Custom', and handle the GridControl.CustomColumnGroup event. To change the text displayed within group rows by default, handle the GridControl.CustomGroupDisplayText event.