The code doc.LoadHtml("http://theurl.com"); will not work. The parameter to LoadHtml should be a string containing HTML, not a URL. You must first fetch the HTML document before trying to parse it.

Once you have the document loaded, for this specific example you can use this:

IEnumerable<string> links = doc.DocumentNode
                               .SelectNodes("//a[@class='tim_new']")
                               .Select(n => n.Attributes["href"].Value);