protected virtual void OnVisibleChanged(ActivityChangedEventArgs e)
        {
            var handler = VisibleChanged;

            if (handler != null)
            {
                handler(this, e);
            }
        }
        protected virtual void OnAllowValidateChanged(ActivityChangedEventArgs e)
        {
            var handler = AllowValidateChanged;

            if (handler != null)
            {
                handler(this, e);
            }
        }