Hazz implements CSS Selectors for HTMLAgilityPack. It is based on Fizzler, a generic CSS Selectors parser and generator library.
Hazz was previously known and distributed as Fizzler.Systems.HtmlAgilityPack.
// Load the document using HTMLAgilityPack as normal
var html = new HtmlDocument();
html.LoadHtml(@"
<html>
<head></head>
<body>
<div>
<p class='content'>Fizzler</p>
<p>CSS Selector Engine</p></div>
</body>
</html>");
// Fizzler for HtmlAgilityPack is implemented as the
// QuerySelectorAll extension method on HtmlNode
var document = html.DocumentNode;
// yields: [<p class="content">Fizzler</p>]
document.QuerySelectorAll(".content");
// yields: [<p class="content">Fizzler</p>,<p>CSS Selector Engine</p>]
document.QuerySelectorAll("p");
// yields empty sequence
document.QuerySelectorAll("body>p");
// yields [<p class="content">Fizzler</p>,<p>CSS Selector Engine</p>]
document.QuerySelectorAll("body p");
// yields [<p class="content">Fizzler</p>]
document.QuerySelectorAll("p:first-child");