When using binding to check state and dynamically adding subitem to a praticular items, the parent items check state is incorrectly set to Off (from ON) although the child item state is also On.

Marking this Declined. Binding to CheckState is not supported in MVVM scenarios. Please use the approach described here =>
http://www.telerik.com/help/wpf/radtreeview-howto-tri-state-mvvm.html