How to highlight numbers in WPF RichTextBox

Question

I'm trying to recolour all the numbers in a WPF RichTextBox to be coloured differently. I've been following this tutorial , but I find that letters in the text are highlighted almost at random. This is the handler I have so far:

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;
}

Answer 1

Try this

DescriptionText.TextChanged -= this.DescriptionText_TextChanged;
var regExp = new Regex(@"^-*[0-9,\.]+$");
foreach (Match match in regExp.Matches(rtb.Text))
    {
        var textRange = rtb.Selection;
        textRange.Select(match.Index, match.Length);
        textRange.ApplyPropertyValue(TextElement.ForegroundProperty, new SolidColorBrush(Colors.Red));
        //rtb.SelectionColor = Color.Red;
    }
DescriptionText.TextChanged += this.DescriptionText_TextChanged;

Answer 2

After making modifications to the questions linked in the comments, I got the following to work: (I've given the relevant codebehind)

public class Tag
{
    public TextPointer StartPosition;
    public TextPointer EndPosition;
}

private void DescriptionText_TextChanged(object sender, TextChangedEventArgs e)
{
    string text;

    DescriptionText.TextChanged -= this.DescriptionText_TextChanged;
    var range = new TextRange(DescriptionText.Document.ContentStart, DescriptionText.Document.ContentEnd);
    range.ClearAllProperties();

    var tags = new List<Tag>();

    TextPointer navigator = DescriptionText.Document.ContentStart;
    while (navigator.CompareTo(DescriptionText.Document.ContentEnd) < 0)
    {
        TextPointerContext context = navigator.GetPointerContext(LogicalDirection.Backward);
        if (context == TextPointerContext.ElementStart && navigator.Parent is Run)
        {
            text = ((Run)navigator.Parent).Text;
            if (text != "")
                tags.AddRange(CheckWordsInRun(text, (Run)navigator.Parent));
        }
        navigator = navigator.GetNextContextPosition(LogicalDirection.Forward);
    }

    foreach (Tag tag in tags)
    {
        var r = new TextRange(tag.StartPosition, tag.EndPosition);
        r.ApplyPropertyValue(TextElement.ForegroundProperty, new SolidColorBrush(Colors.Red));
    }
    DescriptionText.TextChanged += this.DescriptionText_TextChanged;
}

private List<Tag> CheckWordsInRun(string text, Run theRun)
{
    List<Tag> m_tags = new List<Tag>();

    for (int i = 0; i < text.Length; i++)
    {
        if (Char.IsNumber(text[i]))
        {
            Tag t = new Tag();
            t.StartPosition = theRun.ContentStart.GetPositionAtOffset(i, LogicalDirection.Forward);
            t.EndPosition = theRun.ContentStart.GetPositionAtOffset(i + 1, LogicalDirection.Backward);
            m_tags.Add(t);
        }
    }
    return m_tags;
}