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+HTML parsing in .Net is accomplished using one of two popular open-source libraries: [AngleSharp][1] or [HtmlAgilityPack][2]. Of the two, AngleSharp is currently maintained, while HtmlAgilityPack is based off of Microsoft's older XPathNavigator technology and rarely updated.
+
+[1]: https://github.com/AngleSharp/AngleSharp
+[2]: https://htmlagilitypack.codeplex.com/
+
+# AngleSharp
+
+Install via Nuget.
+
+    Install-Package AngleSharp
+
+AngleSharp uses CSS-style selectors.
+
+To get the contents of a tag:
+
+    using AngleSharp.Parser.Html;
+
+   	var htmlDoc = new HtmlParser(html).Parse();
+    var bodyTag = htmlDoc.QuerySelector("body");
+	var bodyContents bodyTag.InnerHtml;
+
+To change an attribute value on a tag:
+
+    var h1Tag = htmlDoc.QuerySelector("h1");
+	h1Tag.SetAttribute("class", "newClass");
+
+To iterate over nodes:
+
+    foreach(var anchor in htmlDoc.QuerySelectorAll("a"))
+    { ... }
+
+# HtmlAgilityPack
+
+Install via NuGet.
+
+    Install-Package HtmlAgilityPack
+
+HtmlAgilityPack uses XPath-style selectors. In most cases, there is a direct correlation to the standard XML library (XmlDocument = HtmlDocument, XmlAttribute = HtmlAttribute, etc.)
+
+To get the contents of a tag:
+
+    using HtmlAgilityPack;
+
+	var htmlDoc = new HtmlDocument();
+    htmlDoc.LoadHtml(html);
+    var bodyTag = htmlDoc.DocumentNode.SelectSingleNode("//body");
+    var bodyContents = bodyTag.InnerHtml;
+
+To change an attribute value on a tag:
+
+    var h1Tag = htmlDoc.DocumentNode.SelectSingleNode("//h1");
+    h1Tag.SetAttributeValue("class", "newClass");
+
+To iterate over nodes (note that you have to do a NULL check first, or you will get an exception if no nodes are found; also note the required explicit variable type declaration in the foreach loop):
+
+    if(htmlDoc.DocumentNode.SelectNodes("//a") != null)
+    {
+	    foreach(HtmlNode anchor in htmlDoc.DocumentNode.SelectNodes("//a"))
+	    { ... }
+    }
+
+Alternately, the NULL check can be skipped by using the null coalesce operation in the foreach loop to create an empty collection.
+
+    foreach(HtmlElement anchor in htmlDoc.SelectNodes("//a") ?? new HtmlNodeCollection(htmlDoc.DocumentElement))
+    {}