Extending functionality of RadGridView's native filter

[Andrey]

My task is not to implement new control, like it is done with IFilteringControl interface, but extend functionality of existing FilteringControl.
As far as I understand it can be done through Behavior class - link below.
http://blogs.telerik.com/blogs/posts/10-01-22/how_to_customize_radgridview_s_default_filtering_control_with_attached_behaviors_silverlight_amp_wpf.aspx
By extending I mean that some additional items must be added to "PART_DistinctValuesList" ListBox, and the logic of comparison must be changed from Equal to StartsWith.
While extending functionality like it was done in article I thought that it might be possible just to construct DistinctValueViewModel List of objects and add this to existing list in DataContext.DistinctValues in other words to FilteringViewModel.
The problem is that ConvertedValue can not be set in DistinctValueViewModel, so list can not be constructed and added to existing one.
Is there any way to solve my problem using this solution without implementing new filter control. Or may be another solution also exists.

Thanks.

[Rossen Hristov]

Hello Andrey,

The easiest way for you would be to implement your own custom filtering control from scratch. The stock one was never designed in order to be widely extensible in any possible way, so it serves its particular job. You can of course study its source code in order to understand what it does. After that it would be easier for you to create your very own custom filtering control. 

I hope this helps.

Greetings,

Ross
the Telerik team