public override string GetStepParameters() { var parameters = new List <string>(); parameters.Add(Curve3D != null ? Curve3D.ToStepValue() : "$"); parameters.Add(AssociatedGeometry != null ? AssociatedGeometry.ToStepValue() : "$"); parameters.Add(MasterRepresentation != null ? MasterRepresentation.ToStepValue() : "$"); return(string.Join(", ", parameters.ToArray())); }