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

Here's how to draw a red circle, with black border on the map in WPF:

public class YourMapControl : GMapControl
{
   protected override void OnRender(DrawingContext drawingContext)
   {
      base.OnRender(drawingContext);

      Point center(40.730610, -73.935242);
      double radius = 0.1;

      drawingContext.DrawEllipse(Brushes.Red, Pens.Black, center, radius, radius);
   }
}

As far as the second part of the question itself, you would use the following built-in MapControl functions:

public bool DisableAltForSelection; //if true, selects area just by holding mouse and moving
public bool SelectionUseCircle; //use circle for selection
public event SelectionChange OnSelectionChange; //occurs when mouse selection is changed
public RectLatLng SelectedArea { get; set; } //returns rect with coordinates of the selected area

Answer 2

My code draws arcs and inherits from GMapMarker too. The arc sweeps from point A to point B with the pivot point at C. Where point A and B are coincidental, a circle will be drawn.

    public class CustomArc : GMapMarker, ISerializable {
    [NonSerialized]
    public Pen pen;

    private int radius = 20;
    private int pen_width = 2;

    private float start = 0.0f;
    private float sweep = 0.0f;

    private GPoint ptA;
    private GPoint ptB;
    private GPoint ptC;
    private List<PointF> points;

    private static Logger logger = LogManager.GetCurrentClassLogger();

    public CustomArc(GPoint ptA, GPoint ptB, GPoint ptC, PointLatLng geo) : base(geo) {
        this.ptA = ptA;
        this.ptB = ptB;
        this.ptC = ptC;
        initialise();
    }

    private void initialise() {
        this.pen = new Pen(Brushes.White, this.pen_width);
        this.radius = (int)UIMaths.distance(ptC, ptA);

        this.points = new List<PointF>();

        if (ptA == ptB) {
            this.sweep = 360.0f;
        } else {
            // Calculate the radius
            this.sweep = (float)UIMaths.sweepAngleDeg(ptA, ptB, ptC);
        }
        this.start = (float)UIMaths.startAngle(ptC, ptB);
        Size = new Size(2 * radius, 2 * radius);
        Offset = new Point(-Size.Width / 2, -Size.Height / 2);

        Console.Out.WriteLine("Radius {0}, Start {1:0.0}, Sweep {2:0.0}", radius, start, sweep);
    }



    public override void OnRender(Graphics g) {
        try {
            Rectangle rect = new Rectangle(LocalPosition.X, LocalPosition.Y, Size.Width, Size.Height);
            g.DrawArc(pen, rect, start, sweep);

        } catch (ArgumentException ex) {
            logger.Error(ex.Message);
        }
    }

    public sealed override void Dispose() {
        if (pen != null) {
            pen.Dispose();
            pen = null;
        }

        base.Dispose();
    }

    #region ISerializable Members

    void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context) {
        base.GetObjectData(info, context);
    }

    protected CustomArc(SerializationInfo info, StreamingContext context)
     : base(info, context) {
    }
    #endregion

}