How to ADD GrandChild Items to Treeview in WPF

Question

+ COUNTRY
            + INDIA
                   AP
                   UP
             +USA
                   Lusiana
                   Nwyrk

how to do this..? Here i am retrieving that data form database, But dont know How to ADD these Items to Root...

Can any one help me with this.... :(

Thank you.

Beginner in WPF......Venu