void polygon_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            if (_pickedSprite != null)
            {
                _pickedSprite.ReleaseMouseCapture();
            }
            if (_mousePickSpring != null && _mousePickSpring.IsDisposed == false)
            {
                _mousePickSpring.Dispose();
                _mousePickSpring = null;

                _lineShowSpring.Visibility = Visibility.Collapsed;

                e.Handled = true;
            }

            if (MouseLeftButtonUp != null && _pickedSprite != null)
            {
                MouseLeftButtonUp(_pickedSprite.Name);
            }

            _pickedSprite = null;
        }