This example demonstrates how to implement sorting in print preview.
For this, handle the PreviewClick event of a column header control (e.g. XRLabel or XRTableCell), then specify a report's sorting options via its Detail.SortFields property, and at last refresh the document by calling the CreateDocument method.
Note: It's also very convenient to store the data field name in the control's Tag property, instead of trying to parse the control's binding.
See also:
Print Preview - How to implement a drop-down menu for sorting report data