public MapPoint this[ 
   int index
]; {get;}

{
    // build a polygon      
    List<MapPoint> pts =
    [
      MapPointBuilderEx.CreateMapPoint(1.0, 1.0),
  MapPointBuilderEx.CreateMapPoint(1.0, 2.0),
  MapPointBuilderEx.CreateMapPoint(2.0, 2.0),
  MapPointBuilderEx.CreateMapPoint(2.0, 1.0),
];

    Polygon poly = PolygonBuilderEx.CreatePolygon(pts);

    // test if an inner point is contained
    MapPoint innerPt = MapPointBuilderEx.CreateMapPoint(1.5, 1.5);
    bool contains = GeometryEngine.Instance.Contains(poly, innerPt);   // contains = true

    // test a point on a boundary
    contains = GeometryEngine.Instance.Contains(poly, poly.Points[0]);     // contains = false

    // test an interior line
    MapPoint innerPt2 = MapPointBuilderEx.CreateMapPoint(1.25, 1.75);
    List<MapPoint> innerLinePts = [innerPt, innerPt2];

    // test an inner polyline
    polyline = PolylineBuilderEx.CreatePolyline(innerLinePts);
    contains = GeometryEngine.Instance.Contains(poly, polyline);   // contains = true

    // test a line that crosses the boundary
    MapPoint outerPt = MapPointBuilderEx.CreateMapPoint(3, 1.5);
    List<MapPoint> crossingLinePts = [innerPt, outerPt];

    polyline = PolylineBuilderEx.CreatePolyline(crossingLinePts);
    contains = GeometryEngine.Instance.Contains(poly, polyline);     // contains = false

    // test a polygon in polygon
    Envelope env = EnvelopeBuilderEx.CreateEnvelope(innerPt, innerPt2);
    contains = GeometryEngine.Instance.Contains(poly, env);      // contains = true
  }