You can use a helper tool to HtmlAgility which would be Fizzler
!!
it has the same purpose as HtmlAgility but in it you can do "query's" on your object to get the desired element,
you can download Fizzler at the same nuget,
and would work like this
WebClient wc = new WebClient();
wc.Headers.Add(HttpRequestHeader.UserAgent, "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.146 Safari/537.36");
string pag = wc.DownloadString("pagina de onde você quer pegar a informação");
HtmlDocument doc = new HtmlDocument();
doc.LoadHtml2(pag);
var tabela = doc.DocumentNode.QuerySelectorAll("tags do queryselector").ToList();
You can search a little more about the queryselector tags and the basics would be
"#" = Element ID,
"." = element class,
and the elements tags in html normally!