public double StartDirection {get; set;}

{
  GeodesicSectorParameter param = new()
  {
    ArcVertexCount = 50,
    AxisDirection = Math.PI / 4,
    Center = new Coordinate2D(0, 0),
    LinearUnit = LinearUnit.Meters,
    OutGeometryType = GeometryType.Polygon,
    RadiusVertexCount = 10,
    SectorAngle = 5 * Math.PI / 3,
    SemiAxis1Length = 100000,
    SemiAxis2Length = 20000,
    StartDirection = 11 * Math.PI / 6
  };

  Geometry geometry = GeometryEngine.Instance.GeodesicSector(param, SpatialReferences.WGS84);
  // geometry.IsEmpty = false

  polygon = geometry as Polygon;
  // polygon.PointCount = 68
  // polygon.PartCount = 1
}