draw_circle.cs

public void DrawCircleOnMap(GeofenceModel geoModel)
{
     if (circle != null)
     {
         circle.Remove();
         circle = null;
     }
     CircleOptions circleOptions = new CircleOptions()
   .InvokeCenter(geoModel.LatLng)
   .InvokeRadius(geoModel.Radius)
   .InvokeFillColor(Color.Argb(50, 0, 14, 84))
   .InvokeStrokeColor(Color.Yellow)
   .InvokeStrokeWidth(15);
     circle = hMap.AddCircle(circleOptions);
}

private void radiusBar_ProgressChanged(object sender, SeekBar.ProgressChangedEventArgs e)
{
  selectedCoordinates.Radius = e.Progress;
  DrawCircleOnMap(selectedCoordinates);
}