If by that, you mean manipulate a DWG file outside of AutoCAD then you will need to purchase RealDWG.
RealDWG is AutoCAD .NET API without interface libraries (reference only acdbmgd.dll, no need accoremgd.dll & acmgd.dll). What ever you can do on AutoCAD for DWG database can be done the same with RealDWG. You can link external database (SQL Server, Oracle...) to 3D entities in DWG files.
If you buy RealDWG license from Tech Soft 3D (official vendor of Autodesk), there is an option to buy additional RealDWG support from Autodesk. As this forum is not for the commercial RealDWG support, it is better to have official Autodesk support. However, it should not be a problem is you have knowledge of AutoCAD .NET API.
ADN is a good starting resource at http://usa.autodesk.com/adsk/servlet/index?siteID=123112&id=770257
Kean's blog: http://through-the-interface.typepad.com/through_the_interface/2008/06/devtv-on-realdw.html
Google also is a very good resource.