protected static void ChangedCallbackCalled(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            Debug.WriteLine("Changed callback called.");

            BaseTestControl control = d as BaseTestControl;

            if (control != null)
            {
                control.IsChangedCallbackCalled = true;
            }
        }
        protected static object CoerceCallbackCalled(DependencyObject d, object o)
        {
            Debug.WriteLine("Coerce callback called.");

            BaseTestControl control = d as BaseTestControl;

            if (control != null)
            {
                control.IsCoerceCallbackCalled = true;
            }

            return(o);
        }