A point group is a collection that defines a subset of the points in a document. Points may be grouped for a number of reasons, such as points that share common characteristics or are used to perform a common task (for example, define a surface). A collection of all point groups in a drawing is held in a document‘s CivilDocument.PointGroups property. Add a new point group by using the CivilDocument.PointGroups.Add() method and specifying a unique identifying string name. The ObjectId for a new, empty point group is returned.
// _civildoc is the active CivilDocument instance.
ObjectId pointGroupId = _civildoc.PointGroups.Add("Example Point Group");
PointGroup pointGroup = pointGroupId.GetObject(OpenMode.ForRead) as PointGroup;