Silverlight Dataform DeleteItem problem

I have a toolbar control in my application. Delete an item from dataform from toolbar delete button. After this apply submitchan开发者_运维问答ges() method. Delete Item work fine but source.HasChange is always false so submitchanges doesn't work fine. no deleting from Database. Plase help thanks..

find your answer in http://cid-1bf46693be07cfa6.office.live.com/self.aspx/.Public/DeleteThroughDataForm.zip sample