HTML Parsing in C# .NET: Best Libraries

HTML Parsing in C# (.NET): Overview of HtmlAgilityPack and AngleSharp Libraries

HTML parsing is one of the key tasks when developing web scrapers, content analyzers, and automation tools. In the C# (.NET) ecosystem, there are several mature libraries that allow you to extract data from HTML documents, manipulate the DOM tree, and perform queries on elements. In this article, we will take a detailed look at the two most popular libraries: HtmlAgilityPack and AngleSharp, their capabilities, syntax, and usage examples.

1. HtmlAgilityPack — A Time-Tested Tool

HtmlAgilityPack (HAP) is one of the oldest and most widely used libraries for HTML parsing in .NET. It supports both .NET Framework and .NET Core / .NET 5+. Its main advantage is simplicity and fault tolerance when working with "dirty" HTML (invalid markup, unclosed tags).

Installation

// Via NuGet Package ManagerInstall-Package HtmlAgilityPack

// Or via .NET CLIdotnet add package HtmlAgilityPack

Basic Example: Extracting H1 Headings

using HtmlAgilityPack;

string html = @"<html><body>    <h1>Heading 1</h1>    <h1>Heading 2</h1>    <p>Paragraph text</p></body></html>";

var doc = new HtmlDocument();doc.LoadHtml(html);

var h1Nodes = doc.DocumentNode.SelectNodes("//h1");if (h1Nodes != null){    foreach (var node in h1Nodes)    {        Console.WriteLine(node.InnerText.Trim());    }}// Output:// Heading 1// Heading 2

Using XPath and CSS Selectors

HtmlAgilityPack uses XPath for navigation by default. However, with the HtmlAgilityPack.CssSelectors package, you can use CSS selectors:

// Installation: dotnet add package HtmlAgilityPack.CssSelectorsusing HtmlAgilityPack.CssSelectors;

// ... after loading the documentvar links = doc.DocumentNode.QuerySelectorAll("a.external-link");foreach (var link in links){    Console.WriteLine(link.GetAttributeValue("href", ""));}

Parsing a Real Website

using System.Net.Http;using HtmlAgilityPack;

var url = "https://example.com/articles";var httpClient = new HttpClient();var html = await httpClient.GetStringAsync(url);

var doc = new HtmlDocument();doc.LoadHtml(html);

// Extract all article headingsvar articles = doc.DocumentNode.SelectNodes("//article/h2/a");if (articles != null){    foreach (var article in articles)    {        var title = article.InnerText.Trim();        var link = article.GetAttributeValue("href", "");        Console.WriteLine($"{title} -> {link}");    }}

2. AngleSharp — A Modern Alternative

AngleSharp is a newer library that offers full support for HTML5, CSS3, JavaScript (limited), and DOM specifications. It is ideal for tasks requiring precise compliance with browser rendering. It supports .NET Standard 2.0+, meaning compatibility with .NET Framework 4.6.1+ and .NET Core.

Installation

dotnet add package AngleSharp

Basic Example: Extracting All Links

using AngleSharp;using AngleSharp.Dom;using AngleSharp.Html.Parser;

var html = @"<html><body>    <a href='https://example.com'>Example</a>    <a href='https://test.com'>Test</a></body></html>";

var parser = new HtmlParser();IDocument document = parser.ParseDocument(html);

var links = document.QuerySelectorAll("a");foreach (var link in links){    Console.WriteLine($"{link.TextContent} -> {link.GetAttribute("href")}");}// Output:// Example -> https://example.com// Test -> https://test.com