How to draw circle on the MAP using GMAP.NET in C#

Question

I am using GMAP.NET in c#. I am able to display the map on the form, now i am trying to draw a CIRCLE mouse by clicking on a certian point, keeping the left mouse button an

Answer 1

        GMapOverlay markers = new GMapOverlay("markers");
        private void CreateCircle(Double lat, Double lon, double radius, int segments)
        {
            markers.Polygons.Clear();
            PointLatLng point = new PointLatLng(lat, lon);

            List gpollist = new List();
            for (int i = 0; i < segments; i++)
                gpollist.Add(FindPointAtDistanceFrom(point, i, radius / 1000));

            List gpollistR = new List();
            List gpollistL = new List();
            foreach (var gp in gpollist)
            {
                if (gp.Lng > lon)
                {
                    gpollistR.Add(gp);
                }
                else
                {
                    gpollistL.Add(gp);
                }
            }
            gpollist.Clear();

            List gpollistRT = new List();
            List gpollistRB = new List();
            foreach (var gp in gpollistR)
            {
                if (gp.Lat > lat)
                {
                    gpollistRT.Add(gp);
                }
                else
                {
                    gpollistRB.Add(gp);
                }
            }
            gpollistRT.Sort(new LngComparer());
            gpollistRB.Sort(new Lng2Comparer());
            gpollistR.Clear();
            List gpollistLT = new List();
            List gpollistLB = new List();
            foreach (var gp in gpollistL)
            {
                if (gp.Lat > lat)
                {
                    gpollistLT.Add(gp);
                }
                else
                {
                    gpollistLB.Add(gp);
                }
            }
            //gpollistLT.Sort(new LngComparer());
            gpollistLB.Sort(new Lng2Comparer());
            gpollistLT.Sort(new LngComparer());
            gpollistL.Clear();


            gpollist.AddRange(gpollistRT);
            gpollist.AddRange(gpollistRB);
            gpollist.AddRange(gpollistLB);
            gpollist.AddRange(gpollistLT);
            GMapPolygon gpol = new GMapPolygon(gpollist, "pol");
            gpol.Stroke = new Pen(Color.Red, 1);
            markers.Polygons.Add(gpol);
        }

        public static GMap.NET.PointLatLng FindPointAtDistanceFrom(GMap.NET.PointLatLng startPoint, double initialBearingRadians, double distanceKilometres)
        {
            const double radiusEarthKilometres = 6371.01;
            var distRatio = distanceKilometres / radiusEarthKilometres;
            var distRatioSine = Math.Sin(distRatio);
            var distRatioCosine = Math.Cos(distRatio);

            var startLatRad = DegreesToRadians(startPoint.Lat);
            var startLonRad = DegreesToRadians(startPoint.Lng);

            var startLatCos = Math.Cos(startLatRad);
            var startLatSin = Math.Sin(startLatRad);

            var endLatRads = Math.Asin((startLatSin * distRatioCosine) + (startLatCos * distRatioSine * Math.Cos(initialBearingRadians)));

            var endLonRads = startLonRad + Math.Atan2(
                          Math.Sin(initialBearingRadians) * distRatioSine * startLatCos,
                          distRatioCosine - startLatSin * Math.Sin(endLatRads));

            return new GMap.NET.PointLatLng(RadiansToDegrees(endLatRads), RadiansToDegrees(endLonRads));
        }

        public static double DegreesToRadians(double degrees)
        {
            const double degToRadFactor = Math.PI / 180;
            return degrees * degToRadFactor;
        }

        public static double RadiansToDegrees(double radians)
        {
            const double radToDegFactor = 180 / Math.PI;
            return radians * radToDegFactor;
        }

and this class

class LngComparer : IComparer
    {
        #region IComparer Members

        public int Compare(PointLatLng x, PointLatLng y)
        {
            if (x == null || y == null)
                throw new ArgumentException("At least one argument is null");
            if (x.Lng == y.Lng)
            {
                if (x.Lat > y.Lat)
                {
                    return 1;
                }
                else if (x.Lat < y.Lat)
                {
                    return -1;
                }
                else
                {
                    return 0;
                }
            }
            if (x.Lng < y.Lng) return -1;
            return 1;
        }

        #endregion
    }
    class Lng2Comparer : IComparer
    {
        #region IComparer Members

        public int Compare(PointLatLng x, PointLatLng y)
        {
            if (x == null || y == null)
                throw new ArgumentException("At least one argument is null");
            if (x.Lng == y.Lng)
            {
                if (x.Lat > y.Lat)
                {
                    return 1;
                }
                else if (x.Lat > y.Lat)
                {
                    return -1;
                }
                else
                {
                    return 0;
                }
            }
            if (x.Lng > y.Lng) return -1;
            return 1;
        }

        #endregion
    }