Treeview search items problem in Silverlight 4/5

Question

Ho All,
i have silverlight treeview search items problem please help me on thos anybody.
i have SL4 Treeview control binding list object data to the treecontrol,now i have one textbox when the user enter the any text into texbox it should be filter the related items from the tree and exapand items matched to searxh textbox
if it not matching then its empty the itemsource.
Please helpm on this anybody.
Advanced thank you.

Regards,
Narasimha