XPATH is your friend 🙂
HtmlDocument doc = new HtmlDocument();
doc.LoadHtml(@"<html><body><p>foo <a href="http://www.example.com">bar</a> baz</p></body></html>");
foreach(HtmlNode node in doc.DocumentNode.SelectNodes("//text()"))
{
Console.WriteLine("text=" + node.InnerText);
}