/// <summary>
/// Create a circular polygon around a mappoint for with a radius in pixels.
/// </summary>
/// <param name="mapPoint">Center of the circle as a mappoint.</param>
/// <param name="pixels">Circle radius in screen pixels.</param>
/// <returns>A polygon geometry.</returns>
private Polygon CreateSearchPolygon(MapPoint mapPoint, int pixels)
{
//get search radius
var screenPoint = MapView.Active.MapToScreen(mapPoint);
var radiusScreenPoint = new System.Windows.Point((screenPoint.X + pixels), screenPoint.Y);
var radiusMapPoint = MapView.Active.ScreenToMap(radiusScreenPoint);
var searchRadius = GeometryEngine.Instance.Distance(mapPoint, radiusMapPoint);
//build a search circle geometry
var cent = new Coordinate2D(mapPoint);
var searchGeom = EllipticArcBuilder.CreateEllipticArcSegment(cent, searchRadius, esriArcOrientation.esriArcClockwise, MapView.Active.Map.SpatialReference);
var searchPB = new PolygonBuilder(new[] { searchGeom });
return searchPB.ToGeometry();
}