This class wraps the AcBrLoop ObjectARX class. 

The BoundaryLoop class is the interface class for brep loops. This class defines the functions that are pertinent to the loop level of a brep, which is not exposed in AutoCAD and thus cannot be directly set to anything meaningful. It is (re)set indirectly by the traversers. 

Loops are secondary brep elements and thus have no associated geometry. They do, however, provide context for parameter space curves.

Autodesk.AutoCAD.BoundaryRepresentation.BrepEntity
    Autodesk.AutoCAD.BoundaryRepresentation.BoundaryLoop

Public sealed Class BoundaryLoop
Inherits BrepEntity

public sealed class BoundaryLoop : BrepEntity;

The intended use of the BoundaryLoop class is to create an BREP-contexted loop for determining the faces that share an edge. 

The subentity path should not be set directly, as loop subentities are not exposed in AutoCAD.