private static void OnKeyboardFocusChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            WatermarkTextBox tb = d as WatermarkTextBox;

            tb.ShowCaret();
            if (tb.KeyboardFocus)
            {
                RoutedEventArgs newEventArgs = new RoutedEventArgs(WatermarkTextBox.KeyboardFocusEvent);
                tb.RaiseEvent(newEventArgs);
            }
        }
        private void TextBox_IsEnabledChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            WatermarkTextBox tb = sender as WatermarkTextBox;

            tb.ShowCaret();
        }