public override DatumTransformation GetInverse()

{
  // Create singleton from wkid
  CompositeGeographicTransformation cgt =
      ArcGIS.Core.Geometry.CompositeGeographicTransformation.Create(108272);
  int count = cgt.Count;    // count = 1

  IList<GeographicTransformation> gts = cgt.Transformations
                                  as IList<GeographicTransformation>;
  gts.Add(ArcGIS.Core.Geometry.GeographicTransformation.Create(1437, false));
  count = cgt.Count;        // count = 2

  // create from an enumeration
  CompositeGeographicTransformation another_cgt =
                ArcGIS.Core.Geometry.CompositeGeographicTransformation.Create(gts);
  GeographicTransformation gt0 = another_cgt[0];
  GeographicTransformation gt1 = another_cgt[1];

  // get the inverse
  CompositeGeographicTransformation inversed_cgt = another_cgt.GetInverse() as CompositeGeographicTransformation;
  // inversed_cgt[0] is same as gt1
  // inversed_cgt[1] is same as gt0

  var wkt = gt0.Wkt;
  // create from string 
  CompositeGeographicTransformation third_cgt =
     ArcGIS.Core.Geometry.CompositeGeographicTransformation.Create(wkt, gt0.IsForward);
  count = third_cgt.Count;        // count = 1

  // create from josn
  string json = cgt.ToJson();
  CompositeGeographicTransformation joson_cgt =
    DatumTransformation.CreateFromJson(json) as CompositeGeographicTransformation;
}