public static void telephoneStateChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            SquareButton button = (SquareButton)d;

            switch (button.TelephoneState)
            {
            case TelephoneState.Available:
                button.BaseColor = Colors.LightBlue;
                break;

            case TelephoneState.InUse:
                button.BaseColor = Colors.LightGreen;
                break;

            case TelephoneState.Hold:
                button.BaseColor = Colors.LightCoral;
                break;
            }
        }
        public static void colorChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            SquareButton button = (SquareButton)d;

            button.GenerateGradients();
        }