C# Parsing HTML: AngleSharp Library Tutorials

When the crawler meets the anti-climbing, proxy IP to the rescue

What is the biggest headache for everyone writing crawlers in C? Nine out of ten programmers will say that the IP blocking! This time we have to invite our savior - proxy IP. today to say that AngleSharp library not only parses HTML quickly and accurately, with ipipgo proxy IP service, directly let the crawler doubled the fighting force.

Five minutes to get AngleSharp basic operation

Let's get real first, the installer goes:

Install-Package AngleSharp

For an example of catching the price of an item, notice how the CSS selector is used:

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 document = await context.OpenAsync("Target URL"); var document = await context.OpenAsync("Target URL"); var document = await context.

var priceNodes = document.QuerySelectorAll(".price-item"); var priceNodes = document.QuerySelectorAll(".price-item"); var priceNodes = document.
foreach (var node in priceNodes)
{
    Console.WriteLine(node.TextContent); }
}

At this time if the site found that you visit frequently, click on the IP block. Don't panic, ouripipgo Proxy IPCome in handy right away.

The secret to giving reptiles an invisibility cloak

Here's the point! Add proxy settings in the OpenAsync method:

var proxy = new ProxyOptions
{
    Type = ProxyType.Http,
    Host = "Proxy address assigned by ipipgo",
    Port = Port number
};

var config = Configuration.
    .WithDefaultLoader()
    .WithProxy(proxy); var config = Configuration.

Remember to stuff the request header with the account password provided by ipipgo:

var headers = new Dictionary
{
    { "Proxy-Authorization", "Basic " + Convert.ToBase64String(Encoding.ASCII.GetBytes("Account:Password"))}
};

Practical Tips and Tricks

Frequently Asked Questions QA for Veteran Drivers

Q: What should I do if my proxy IP suddenly fails?
A: hurry to change ipipgo's automatic rotation function, it is recommended to choose their enterprise version of the package, IP pool update speed thief.

Q: How can I tell if a proxy is in effect?
A: Add a test in the code to see if the returned IP is a proxy IP:

var checkDoc = await context.OpenAsync("http://ip.ipipgo.com/");
Console.WriteLine(checkDoc.Body.TextContent);

Q: What should I do if I have to handle multiple websites at the same time?
A: Use ipipgo's concurrent proxy feature with AngleSharp's parallel processing, and remember to set a reasonable request interval.

Guide to avoiding the pit

Three common mistakes newbies make:

1. Proxy IP expired and still dying (use ipipgo's expiration reminder feature)
2. No User-Agent in the request header (easily recognized as a bot)
3. Ignore SSL certificate validation (some sites block it)

As a final rant, you have to keep your eyes peeled when choosing a proxy service provider. The likes ofipipgoThis kind of real-time monitoring of IP availability, use it really save heart. Their API docking documents are written in detail, and specialized technical customer service is always on standby, not afraid of encountering problems no one to take care of.