public ZoneEnvelopeViewModel(IDFCommand zone, IDFDatabase idf)
     : base(null, true)
 {
     _idf = idf;
         _zoneEnvelope = zone;
 }
 public SurfaceEnvelopeViewModel(IDFCommand surface, ZoneEnvelopeViewModel parentZone, IDFDatabase idf)
     : base(parentZone, false)
 {
     _idf = idf;
         _surface = surface;
 }