The ObjRef type exposes the following members.
Gets the component index of the referenced (sub) geometry. Some objects have sub-objects that are valid pieces of geometry. For example, breps have edges and faces that are valid curves and surfaces. Each sub-object has a component index that is > 0. The parent geometry has a component index = -1.
Returns the id of the referenced Rhino object.
If > 0, then this is the value of a Rhino object's serial number field. The serial number is used instead of the pointer to prevent crashes in cases when the RhinoObject is deleted but an ObjRef continues to reference the Rhino object. The value of RuntimeSerialNumber is not saved in archives because it generally changes if you save and reload an archive.