How to query domain without exposing it

Question

Hi, I have a problem. I am building a query engine for the gui consumer. So I have an silverlight application that does not expose Domain entities but rather use DTO objects. On the UserInterace I only have DTO's not the domain entities, so I cant create query like this: Query.AddCriteria(new EqualsCriteria((Person p)=>p.Name, "John");

So on the UI I can only use DTOs like this: Query.AddCriteria(new EqualsCriteria((PersonDTO p)=>p.Name, "John");

But then how to convert this query to the real domain query.

Please any suggestion on how to best implement this is appreciated. Thanks.