/// <summary>
        /// fires when the passwordBox  password values changes
        /// </summary>
        /// <param name="sender"> the ui element that has property changed</param>
        /// <param name="e">event args</param>
        private void PasswordBox_PasswordChanged(object sender, RoutedEventArgs e)
        {
            //set the attached HasText Value
            HasTextProperty.SetValue((PasswordBox)sender);

            //set the BoundPassword Property
            BoundPasswordProperty.SetValue((PasswordBox)sender);
        }
        public override void OnValueChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            //get the caller
            var passwordBox = sender as PasswordBox;

            if (passwordBox == null)
            {
                return;
            }

            //remove any previous event listener
            passwordBox.PasswordChanged -= PasswordBox_PasswordChanged;

            //if the caller set Monitor to true
            if ((bool)e.NewValue)
            {
                // set default value
                HasTextProperty.SetValue(passwordBox);

                passwordBox.PasswordChanged += PasswordBox_PasswordChanged;
            }
        }