C# HTML Parsing: AngleSharp Library Tutorials

What is the AngleSharp library? Why do I need it for HTML parsing?

We do data collection brother must have encountered this kind of shit: the target site page structure is as complex as a spider's web, manual pick data can be tired out of tendinitis. At this time we have to rely on AngleSharp this magic tool, it can be like a bull like the HTML document split into clear. Than the traditional regular expression to save ten times, especially when dealing with nested tags, that is called a silky smooth.

To give a chestnut, want to capture the price data of an e-commerce platform, using traditional methods may have to write dozens of lines of circular judgment. But with AngleSharp as long as three lines of code will be able to lock the target element. More absolute is that it supports the latest CSS selector syntax, people who have used it said that like the opening of the Sharpshooter.

// As a code snippet for a real scenario
var config = Configuration.Default.WithDefaultLoader(); var context = BrowsingContext.New(config); var context = BrowsingContext.
var context = BrowsingContext.New(config); var document = await context.OpenAsync("Target URL"); var context = BrowsingContext.
var document = await context.OpenAsync("Target URL"); var priceNodes = document.
var priceNodes = document.QuerySelectorAll("div.price-box span.final-price");

How do proxy IPs and AngleSharp get in the mix?

The point is! Many websites have anti-climbing mechanism, direct hard just minutes to block your IP, this time to let ipipgo proxy IP service on the show. We can change like a vest, each request for a different IP address, so that the target site thinks it is a different user to visit.

Here's a tawdry maneuver: inject the proxy settings directly into AngleSharp's request flow. Use the API provided by ipipgo to get a fresh proxy IP, and then configure it into the HttpClient. This way, each request will automatically go through the proxy channel, which is much more stable than going it alone.

// Access to the ipipgo proxy in practice code
var handler = new HttpClientHandler
var handler = new HttpClientHandler {
    Proxy = new WebProxy("http://user:pass@ipipgo-proxy-server:port")
};

var httpClient = new HttpClient(handler); var requester = new HttpClientRequester(handler)
var requester = new HttpClientRequester(httpClient); var config = Configuration.
var config = Configuration.Default.WithRequester(requester); var config = Configuration.

Three Tips to Prevent Blocking

The first style: IP rotation method Through ipipgo's API to get a new IP pool at regular intervals, it is recommended to change a batch of IPs every 50 requests, like playing chicken to change the equipment as diligently as

Style 2: Requesting Tempo Control Don't send wild requests like a starving man, give random delays. Suggest a base interval of 1.3 seconds, with a 0-3 second random number stacked on top to make the access pattern more like real people

Style 3: Header camouflage User-Agent is randomly generated for each request, you can use the browser fingerprinting library provided by ipipgo to disguise the request header as various browsers

Practical QA: the pitfalls you may encounter

Q: Why is the parsed data always wrong?
A: 80% of the page is not loaded on the beginning of the parse, remember to use await document.OpenAsync () to ensure that the loading is complete. Remember to use await document.OpenAsync() to make sure it's loaded. If you're using dynamically loaded pages, you'll have to use AngleSharp's Scripting extension.

Q: What should I do if my proxy IP suddenly fails?
A: In this case, it is recommended to use ipipgo's smart switching mode, their API will automatically weed out failed nodes. Remember to add try-catch in the code to trigger the IP replacement process if you encounter a connection exception

Q: How to improve the resolution speed?
A: Three great tips: 1) Parallelize with Parallel.ForEach 2) Pre-compile CSS selectors 3) Use ipipgo's exclusive high-speed lines, which are more than twice as fast as shared pools

Performance Optimization Form

Lastly, I'd like to say that data collection is like guerrilla warfare, and you need to be technically proficient as well as have the tools at your fingertips. With AngleSharp + ipipgo's combo, basically can sweep 90% collection needs. Remember to comply with the rules of the site, we only do serious data analysis, do not organize those tawdry operations.