RadControls for ASP.NET AJAX
You can have complete control over the display of the fields in a GridGroupHeaderItem and even perform calculations and display the results in the group header.
To change the string that appears in the group header, set the DataCell.Text property of the GridGroupHeaderItem instance.
The DataItem property of the GridGroupHeaderItem lets you access the column values you might want to display in the header. The DataItem of GridGroupHeaderItem is always of type DataRowView and contains all the columns that represent fields from the GridGroupByExpression for the group. These include both the fields that are included in the SelectFields collection and the fields that are included in the GroupByFields collection. For a description of the GridGroupByExpression object, see Declarative definition.
You can access the values for the fields in the DataItem by indexing on the name of the field. If you have assigned an alias to the field (set the FieldAlias property of the GridgroupByField), then you must index using the alias rather than the field name.
The following example illustrates how you can customize the formatting of the group header using the grid's ItemDataBound event: