WPF

public new string Text
{
    get { return (string)GetValue(TextProperty); }
    set { SetValue(TextProperty, value); }
}

public new static readonly DependencyProperty TextProperty =
    DependencyProperty.Register("Text", typeof(string),
    typeof(HighlightTextBlock), new FrameworkPropertyMetadata(string.Empty, FrameworkPropertyMetadataOptions.AffectsRender,
        new PropertyChangedCallback(UpdateHighlighting)));

private static void UpdateHighlighting(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    ApplyHighlight(d as HighlightTextBlock);
}