public bool LightUp(GrabControl grabControl)
        {
            if (this == grabControl.ParentControl)
            {
                this.ellipse1.Stroke = new SolidColorBrush(Colors.Red);
                return false;
            }

            foreach (Arrow arrow in this.arrowsIn)
            {
                if (arrow.TailControl == grabControl.ParentControl)
                {
                    this.ellipse1.Stroke = new SolidColorBrush(Colors.Red);
                    return false;
                }
            }

            this.ellipse1.Stroke = new SolidColorBrush(Colors.Green);
            return true;
        }
 public void LightOut(GrabControl grabControl)
 {
     this.ellipse1.Stroke = new SolidColorBrush(LightBlue);
 }