Sources of Information
Before You Begin
AutoCAD Map 3D ObjectARX Developer's Guide describes how to use ObjectARX classes to automate and extend AutoCAD Map 3D.
AutoCAD Map 3D ObjectARX extends AutoCAD ObjectARX into the AutoCAD Map 3D domain.
The ObjectARX and ObjectARX .NET APIs each cover most of AutoCAD Map 3D functionality. But they don't cover Resource Service, Feature Service, or Mapping Service. These areas are covered by the Geospatial Platform API, which is exposed as .NET only.