This class represents a constrained datum unbounded line node in the owning Assoc2dConstraintGroup. 

It is read-only and for reference as datum line, e.g., X datum line and Y datum line.

Autodesk.AutoCAD.DatabaseServices.ConstraintGroupNode
    Autodesk.AutoCAD.DatabaseServices.ConstrainedGeometry
        Autodesk.AutoCAD.DatabaseServices.ConstrainedCurve
            Autodesk.AutoCAD.DatabaseServices.ConstrainedLine
                Autodesk.AutoCAD.DatabaseServices.ConstrainedConstructionLine
                    Autodesk.AutoCAD.DatabaseServices.ConstrainedDatumLine

Public Class ConstrainedDatumLine
Inherits ConstrainedConstructionLine

public class ConstrainedDatumLine : ConstrainedConstructionLine;