bind Combobox from another Combobox MVVM with WCF Ria

Question

Hi, Please give me code for how to bind one combobox to another combobox using silverlight wcf ria services with entity framework.

These combobox get populated by table in database. On basis of first combobox, second combobox gets populated having matching values in table.

How to do this task with MVVM using Entity framework.

Please help me!!

Thanks

Raman