Building a query to access CRM

There is no information on this around the web.
As anyone managed to successfully build a query to access CRM through the WebService using RetrieveMultipleRequest ?

I’ve been able to do this on a normal C# Windows application type project, but on Biztalk, i’m still not able to do this, because it doesn’t let e use a queryexpression type access (like on the C# project, and as is in the SDK).

Instead I have to use a querybase type access, and this way there are fields that I have no ideia what information to map.