public static void Reverse(Esri.ArcGISRuntime.Geometry.PointCollection pts)
{
IEnumerable<MapPoint> reversedPts = pts.Reverse();
Esri.ArcGISRuntime.Geometry.PointCollection newPts =
new Esri.ArcGISRuntime.Geometry.PointCollection();
foreach (MapPoint pt in reversedPts)
newPts.Add(pt);
pts.Clear();
foreach (MapPoint pt in newPts)
pts.Add(pt);
}