You could use the Html Agility Pack library, with a code like this:

        HtmlDocument doc = new HtmlDocument();
        doc.Load(myHtmlFile); // load your file

        // select recursively all A elements declaring an HREF attribute.
        foreach (HtmlNode node in doc.DocumentNode.SelectNodes("//a[@href]"))
        {
            node.ParentNode.ReplaceChild(doc.CreateTextNode(node.InnerText + " <" + node.GetAttributeValue("href", null) + ">"), node);
        }

        doc.Save(Console.Out); // output the new doc.