File Explorer tree view with checkbox for select multiple pa

Question

Hi i am developing one WPF file explorer tree and i am using following approach 

http://www.codeproject.com/Articles/21248/A-Simple-WPF-Explorer-Tree, there is one more this i want to implement is that i want to add check box in it so that user can select multiple path and if user check any folder all its child folders are also get check. i added one checkbox in its template but i am not able to checked all child if parent folder is checked.

please help me.