title: Silverlight: Should I be using IDataErrorInfo, INotifyDataErrorInfo, or both?
body: <p>Should I be using IDataErrorInfo, INotifyDataErrorInfo, or both?</p>
  
  <p>If I use both, should I offer the same error in both or should I only offer sync errors from IDataErrorInfo and only async errors from INotifyDataErrorInfo?</p>