1. Environment Setup
1. Reference Approaches
Two mainstream approaches:
- Legacy approach: Manually import
HtmlAgilityPack.dll - Recommended approach: Install via NuGet package
Install-Package HtmlAgilityPack2. Frequently‑used Core Classes
| Class Name | Purpose |
|---|---|
HtmlDocument | HTML document container, responsible for loading HTML source |
HtmlWeb | Network request class, fetch webpage HTML directly from URL |
HtmlNode | Single HTML DOM node (div/a/p and other tags) |
HtmlNodeCollection | HtmlNode collection for multi‑item query results |
2. Two Ways to Load HTML
Both will produce an HtmlDocument object
1: Load Local File / HTML String
- Load local HTML file
using HtmlAgilityPack;
using System.Text;
HtmlDocument document = new HtmlDocument();
// Load local file with specified encoding
document.Load("news.htm", Encoding.UTF8);Code language: JavaScript (javascript)- Load HTML text string
string htmlStr = "<html>...</html>";
document.LoadHtml(htmlStr);Code language: HTML, XML (xml)2: Load Webpage Online
HtmlWeb web = new HtmlWeb();
HtmlDocument doc = web.Load("https://example.com");Code language: JavaScript (javascript)3. Node Querying
// 1. Instantiate document object
HtmlDocument document = new HtmlDocument();
// 2. Read local html file
document.Load("news.htm", Encoding.UTF8);
// 3. Get document root node
HtmlNode rootNode = document.DocumentNode;
// 4. Batch‑query nodes with XPath, return node collection
HtmlNodeCollection newsList = rootNode.SelectNodes(
@"//html/body/div[@class='content']/div/div[@class='left']/div[1]/div[@class='blk12']/div[@class='blk122']/a"
);Code language: JavaScript (javascript)Key Method Reference
SelectSingleNode("XPath")：Get the first matching node, returnsHtmlNodeSelectNodes("XPath")：Get all matching nodes, returnsHtmlNodeCollection- Course materials show full absolute paths. In real‑world projects, global relative lookup is preferred to simplify XPath and lower breakage risk when page markup changes:
//div[@class='blk122']/aCode language: JSON / JSON with Comments (json)4. Traverse & Extract Content Example
if(newsList != null)
{
foreach(HtmlNode aNode in newsList)
{
string title = aNode.InnerText; // Get text inside tag
string link = aNode.GetAttributeValue("href",""); // Read href attribute
}
}Code language: PHP (php)5. Quick Reference for Important Properties
.InnerText：Plain text inside element.InnerHtml：Inner HTML source including child tags.OuterHtml：Current tag plus its full inner HTML markupGetAttributeValue("AttributeName","DefaultValue")：Safely read tag attributes
Practical Usage
Previous: XPath