void OnZoomStarted(object sender, C1ZoomStartedEventArgs e)
 {
     _dragHelper.Complete();
     _initialZoom      = GetZoom();
     _initialPosition  = GetPosition();
     _relativePosition = e.GetPosition(Rectangle);
 }
 void OnZoomStarted(object sender, C1ZoomStartedEventArgs e)
 {
     _dragHelper.Complete();
     _initialZoom          = GetZoom();
     _initialPosition      = GetPosition();
     _relativePosition     = e.GetPosition(Rectangle);
     Rectangle.BorderBrush = new SolidColorBrush(Colors.YellowGreen);
 }