This class represents a radius or diameter constraint node in the owning Assoc2dConstraintGroup. 

It can be applied on one circle(arc) or ellipse(bounded ellipse).

Autodesk.AutoCAD.DatabaseServices.ConstraintGroupNode
    Autodesk.AutoCAD.DatabaseServices.GeometricalConstraint
        Autodesk.AutoCAD.DatabaseServices.ExplicitConstraint
            Autodesk.AutoCAD.DatabaseServices.RadiusDiameterConstraint

Public Class RadiusDiameterConstraint
Inherits ExplicitConstraint

public class RadiusDiameterConstraint : ExplicitConstraint;