Agility Pack Decendant function issue

[HarisRiaz]

public string getContent(string webAddress)
{
HtmlAgilityPack.HtmlWeb web = new HtmlAgilityPack.HtmlWeb();
HtmlDocument doc = web.Load(webAddress);
return string.Join(" ", doc.DocumentNode.Descendants().Select(x => x.InnerText));
}
Am using this function trying to check what does the function do! But am getting the exception which tells me the function Decendants does not exist in the current context! Though i have included the refrenced dll of agility pack!