public static List<Coordinate> generateCirclePoints(double centerLat, double centerLon, double radius)
        {
            int iBearing;
            double[] lonArray = new double[360];
            double[] latArray = new double[360];
            List<Coordinate> coords = new List<Coordinate>();
            for (iBearing = 0; iBearing < 360; iBearing++)
            {
                calcNewPosition(centerLat, centerLon, iBearing, radius, out latArray[iBearing], out lonArray[iBearing]);
                coords.Add(new Coordinate { lat = latArray[iBearing], lon = lonArray[iBearing] });
            }

            return coords;
        }

        private static double radians(double x)
        {
            return Math.Acos(0.0) * x / 90.0;
        }

        private static void calcNewPosition(double lat, double lon, double bearing, double d, out double newLat,
            out double newLon)
        {
            double lat1, lon1, br, pi;
            double Re = 6371000;
            // convert everything to radians first:
            lat1 = radians(lat);
            lon1 = radians(lon);
            br = radians(bearing);

            pi = 2 * Math.Acos(0.0);

            double lat2, lon2;
            lat2 = Math.Asin(Math.Sin(lat1) * Math.Cos(d / Re) +
                             Math.Cos(lat1) * Math.Sin(d / Re) * Math.Cos(br));
            lon2 = lon1 + Math.Atan2(Math.Sin(br) * Math.Sin(d / Re) * Math.Cos(lat1),
                Math.Cos(d / Re) - Math.Sin(lat1) * Math.Sin(lat2));
            newLat = 180.0 * lat2 / pi;
            newLon = 180.0 * lon2 / pi;
        }

    public class Circle : Polygon
    {
        private double radius = double.NaN;
        private MapPoint center;
        private int pointCount = 360;

        private readonly ESRI.ArcGIS.Client.Projection.WebMercator mercator =
            new ESRI.ArcGIS.Client.Projection.WebMercator();

        public double Radius
        {
            get { return radius; }
            set { radius = value; CreateRing(); }
        }

        [System.ComponentModel.TypeConverter(typeof(MapPointConverter))]
        public MapPoint Center
        {
            get { return center; }
            set { center = value; CreateRing(); }
        }

        public int PointCount
        {
            get { return pointCount; }
            set { pointCount = value; CreateRing(); }
        }

        private void CreateRing()
        {
            Rings.Clear();
            if (!double.IsNaN(Radius) && Radius > 0 && Center != null && PointCount > 2)
            {
                PointCollection pnts = new PointCollection();

                foreach (var coord in MapMaths.generateCirclePoints(center.X, center.Y, radius))
                {
                    Geometry geomPoint = mercator.FromGeographic(new MapPoint(coord.lon, coord.lat));
                    pnts.Add(new MapPoint(geomPoint.Extent.XMax, geomPoint.Extent.YMax));
                }
                //for (int i = 0; i <= PointCount; i++)
                //{
                //    double rad = 2 * Math.PI / PointCount * i;
                //    double x = Math.Cos(rad) * radius + Center.X;
                //    double y = Math.Sin(rad) * radius + Center.Y;
                //    pnts.Add(new MapPoint(x, y));
                //}
                Rings.Add(pnts);
            }
        }
    }