问如何在WPF RichTextBox中突出显示数字

EN

private void DescriptionText_TextChanged(object sender, TextChangedEventArgs e)
{
    var range = new TextRange(DescriptionText.Document.ContentStart, DescriptionText.Document.ContentEnd);
    var regex = new Regex("[0-9]+");
    var num_ranges = new List<TextRange>();

    // add all the ranges with numbers
    foreach (Match match in num_reg.Matches(range.Text))
    {
        var start = range.Start.GetPositionAtOffset(match.Index);
        var end   = range.Start.GetPositionAtOffset(match.Index + match.Length);

        num_ranges.Add(new TextRange(start, end));
    }

    // unsuscribe before making changes
    DescriptionText.TextChanged -= this.DescriptionText_TextChanged;

    range.ClearAllProperties();
    range.ApplyPropertyValue(TextElement.ForegroundProperty, new SolidColorBrush(Colors.Black));

    foreach (var r in num_ranges)
    {
        r.ApplyPropertyValue(TextElement.ForegroundProperty, new SolidColorBrush(Colors.Red));
    }

    DescriptionText.TextChanged += this.DescriptionText_TextChanged;
}