How do I handle errors or exceptions when using IronWebScraper?

IronWebScraper is a C# library designed to make web scraping simple. It provides many features to streamline the scraping process, including built-in error handling. Exceptions and errors can occur during a web scraping process for various reasons, such as network issues, changes in the target website's structure, or access restrictions.

To handle errors in IronWebScraper, you can use try-catch blocks around your scraping code, or you can utilize the in-built event handlers provided by the IronWebScraper API. Below is an example of how to handle errors using IronWebScraper in a C# application.

using IronWebScraper;
using System;

class Program
{
    static void Main(string[] args)
    {
        var scraper = new WebScraper();

        // Set up the OnError event handler to catch any errors during the scraping process
        scraper.OnError += (s, e) =>
        {
            Console.WriteLine("An error occurred: " + e.Message);
            if (e.InnerException != null)
            {
                Console.WriteLine("Inner Exception: " + e.InnerException.Message);
            }
            // You can log the error, retry the request, or take other appropriate actions
        };

        // Set up the rest of your scraping logic
        scraper.Request("https://example.com", Parse);

        // Start the scraping process
        scraper.Start();
    }

    // Define the parsing method that will be used when the page is successfully fetched
    public static void Parse(Response response)
    {
        try
        {
            // Your parsing logic goes here
            // For example: response.Css("a.some-class");
        }
        catch (Exception ex)
        {
            // Handle any exceptions that occur during parsing
            Console.WriteLine("An exception occurred during parsing: " + ex.Message);
        }
    }
}

In the above example, we attach an event handler to the OnError event of the WebScraper instance. This event is triggered whenever an error occurs during the scraping process. You can log the error, attempt to retry the request, or perform any other error handling logic within this event handler.

In the Parse method, you can also use try-catch blocks to handle any exceptions that might occur while processing the fetched data. This allows you to handle parsing-specific errors separately from network-related errors.

When handling errors, you should consider how to deal with different types of exceptions. For example, you might want to implement different logic for HTTP errors (like 404 Not Found or 503 Service Unavailable) compared to other exceptions such as parsing errors or timeouts.

IronWebScraper also allows you to customize retry logic. If you want to automatically retry requests that fail due to transient network issues, you can configure retry options when setting up your scraper:

scraper.Request("https://example.com", Parse, new RequestOptions
{
    RetryCount = 3, // Number of retries on failure
    RetryDelay = 1000, // Delay between retries in milliseconds
});

Remember to always respect the target website's robots.txt file and terms of service to avoid any legal or ethical issues. Also, consider implementing polite scraping practices such as rate limiting and providing a User-Agent string that identifies your scraper.