public double ShapePreservingLength( 
   Geometry geometry,
   LinearUnit lengthUnit
)

{
  // pt
  MapPoint pt = MapPointBuilderEx.CreateMapPoint(1.0, 3.0, SpatialReferences.WebMercator);
  double len = GeometryEngine.Instance.ShapePreservingLength(pt);          // len = 0

  List<MapPoint> pts =
  [
    MapPointBuilderEx.CreateMapPoint(1.0, 1.0, 3.0),
  MapPointBuilderEx.CreateMapPoint(1.0, 3.0, 3.0),
  MapPointBuilderEx.CreateMapPoint(3, 3, 3.0),
  MapPointBuilderEx.CreateMapPoint(3.0, 1.0, 3.0),
];

  // multipoint
  Multipoint mPt = MultipointBuilderEx.CreateMultipoint(pts);
  len = GeometryEngine.Instance.ShapePreservingLength(mPt);                // len = 0

  // polyline
  polyline = PolylineBuilderEx.CreatePolyline(pts, SpatialReferences.WGS84);
  len = GeometryEngine.Instance.ShapePreservingLength(polyline);

  // polygon
  polygon = PolygonBuilderEx.CreatePolygon(pts, SpatialReferences.WGS84);
  len = GeometryEngine.Instance.ShapePreservingLength(polygon);

  polyline = PolylineBuilderEx.CreatePolyline(
  [
    MapPointBuilderEx.CreateMapPoint( -170, 0),
  MapPointBuilderEx.CreateMapPoint( 170, 0)
  ], SpatialReferences.WGS84);


  var length_meters = GeometryEngine.Instance.ShapePreservingLength(polyline); // , LinearUnits.Meters);
  var length_miles = GeometryEngine.Instance.ShapePreservingLength(polyline, LinearUnit.Miles);

  // length_meters - 37848626.869713023
  // length_miles - 23518.046402579574
}