With entities you get built-in validation, so with non-entities you have to drive the validation yourself.  In your property setter you can call VerifierEngine.ExecuteBeforeSet and/or ExecuteAfterSet for the property in question.  To perform instance-level validation you call VerifierEngine.Execute.  A VerifierEngine can be created standalone, or you can use your EntityManager's.  You can use standard DevForce validation attributes on non-entities, and also create custom verifiers.

 

Although we don't have a sample, we do make use of non-entity validation in the DevForce Silverlight Business Application template.  If you've used that, the VerifiableObject class defined there serves as the base class for non-entity classes requiring verification.  The VerifiableObject also implements INotifyPropertyChanged and INotifyDataErrorInfo.  You can see this code in action if you create a new solution from this template, or I can upload the class if you're interested.

 

For the record, our validation documentation is here - http://drc.ideablade.com/xwiki/bin/view/Documentation/validate