This example demonstrates how to create and apply a custom filtering control for RadGridView.
See also:
WPF: http://docs.telerik.com/devtools/wpf/controls/radgridview/filtering/how-to/howto-create-a-custom-field-filter-editor
SL: http://docs.telerik.com/devtools/silverlight/controls/radgridview/filtering/how-to/howto-create-a-custom-field-filter-editor