Modifying InnerXml of a text XmlNode

Question

I traverse an html document with SGML and XmlDocument. When I find an XmlNode which its type is Text, I need to change its value that has an xml element. I can't change InnerXml because it's readonly. I tried to change InnerText, but this time tag descriptor chars < and > encoded to < and >. for example:

<p>
    This is a text that will be highlighted.
    <anothertag />
    <......>
</p>

I'm trying to change to:

<p>
    This is a text that will be <span class="highlighted">highlighted</span>.
    <anothertag />
    <......>
</p>

What is the easiest way to modify the value of a text XmlNode?

Answer 1

I have a workaround, I don't know it is a real solution or what, but it can result what I want. Please comment for this code if it is worthy solution or not

    private void traverse(ref XmlNode node)
    {
        XmlNode prevOldElement = null;
        XmlNode prevNewElement = null;
        var element = node.FirstChild;
        do
        {
            if (prevNewElement != null && prevOldElement != null)
            {
                prevOldElement.ParentNode.ReplaceChild(prevNewElement, prevOldElement);
                prevNewElement = null;
                prevOldElement = null;
            }
            if (element.NodeType == XmlNodeType.Text)
            {
                var el = doc.CreateElement("text");
                //Here is manuplation of the InnerXml.
                el.InnerXml = element.Value.Replace(a_search_term, "<b>" + a_search_term + "</b>");
                //I don't replace element right now, because element.NextSibling will be null.
                //So I replace the new element after getting the next sibling.
                prevNewElement = el;
                prevOldElement = element;
            }
            else if (element.HasChildNodes)
                traverse(ref element);
        }
        while ((element = element.NextSibling) != null);
        if (prevNewElement != null && prevOldElement != null)
        {
            prevOldElement.ParentNode.ReplaceChild(prevNewElement, prevOldElement);
        }

    }

Also, I remove <text> and </text> strings after the traverse function:

        doc = new XmlDocument();
        doc.PreserveWhitespace = true;
        doc.XmlResolver = null;
        doc.Load(sgmlReader);
        var html = doc.FirstChild;
        traverse(ref html);
        textBox1.Text = doc.OuterXml.Replace("<text>", String.Empty).Replace("</text>", String.Empty);