Hello Henk Boen,
There is no way to expose just some desired fields out of the box. As a workaround though, I could suggest you make a hierarchy for the classes that you do not want fully exposed on the client side of the ADO .NET Dataservice. In that case you can put the fields you want exposed in the base class and the rest in the derived class. That way you can manipulate the visibility of your fields in different scenarios.
the Telerik team