On a Silverlight 2 datagrid, how can I get a collection of only the rows that are edited?

I load data into my grid using a WCF service. When a user clicks 'Submit' on my silverlight 2 control, I want to send only the edited rows back to my WCF service for updating. Is there a good way to do this?

From stackoverflow

• Its better if you monitor the changes on the source objects. It would be easy to write a simple class to register for the changes using the INotifyPropertyChange and keep a list of changed objects (the sources).

  Scott : thanks Shawn. The class I am binding from implements INotifyPropertyChanged automatically. Are you suggesting to write another class? I'm not sure where that fits in