Quick Start: C# / .NET

Make your first API call with C# and parse the HTML response with AngleSharp.

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Prerequisites

.NET 6.0+ (for top-level statements and System.Net.Http.Json)
A FastWebScraper API key (get one free)

Installation

Install AngleSharp for HTML parsing. HttpClient and System.Net.Http.Json are built into .NET 6+.

dotnet add package AngleSharp

Sync Scraping (Simple)

The sync endpoint waits for the scrape to complete and returns the HTML in a single response. Best for quick scripts and testing.

// Program.cs
using System.Net.Http.Json;
using System.Text.Json;

using var client = new HttpClient { Timeout = TimeSpan.FromSeconds(60) };
client.DefaultRequestHeaders.Add("X-API-Key", "YOUR_API_KEY");

var request = new
{
    url = "https://example.com",
    mode = "auto"
};

var response = await client.PostAsJsonAsync("https://api.fastwebscraper.com", request);

if (!response.IsSuccessStatusCode)
{
    var error = await response.Content.ReadAsStringAsync();
    Console.WriteLine($"Error: {error}");
    return;
}

var result = await response.Content.ReadFromJsonAsync<JsonElement>();
var data = result.GetProperty("data");

Console.WriteLine($"Status code: {data.GetProperty("statusCode")}");
Console.WriteLine($"HTML length: {data.GetProperty("html").GetString()?.Length}");

Async Scraping (Production)

The async endpoint returns a job ID immediately. Poll for the result when it's ready. Use this for production workloads and batch processing.

// Program.cs
using System.Net.Http.Json;
using System.Text.Json;

using var client = new HttpClient();
client.DefaultRequestHeaders.Add("X-API-Key", "YOUR_API_KEY");

// Step 1: Submit the scrape job
var request = new
{
    url = "https://example.com",
    mode = "auto",
    waitForSelector = ".main-content"
};

var submitResponse = await client.PostAsJsonAsync("https://api.fastwebscraper.com", request);
var submitResult = await submitResponse.Content.ReadFromJsonAsync<JsonElement>();
var jobId = submitResult.GetProperty("data").GetProperty("jobId").GetString();
Console.WriteLine($"Job submitted: {jobId}");

// Step 2: Poll for the result
JsonElement job;
string status;
do
{
    await Task.Delay(2000);
    job = await client.GetFromJsonAsync<JsonElement>(
        $"https://api.fastwebscraper.com/{jobId}");
    status = job.GetProperty("data").GetProperty("status").GetString()!;
    Console.WriteLine($"Status: {status}");
} while (status is "PENDING" or "IN_PROGRESS");

if (status == "COMPLETED")
{
    var html = job.GetProperty("data").GetProperty("html").GetString()!;
    Console.WriteLine($"HTML length: {html.Length}");
}
else
{
    Console.WriteLine("Job failed");
}

Parsing HTML with AngleSharp

Once you have the HTML, use AngleSharp to extract structured data. AngleSharp provides a standards-compliant HTML parser with a DOM API similar to browser JavaScript.

using AngleSharp;
using AngleSharp.Html.Parser;

// Assuming 'html' contains the scraped HTML string
var parser = new HtmlParser();
var document = await parser.ParseDocumentAsync(html);

// Extract text content
var pageTitle = document.QuerySelector("h1")?.TextContent.Trim();
Console.WriteLine($"Page title: {pageTitle}");

// Extract all links
var links = document.QuerySelectorAll("a[href]")
    .Select(a => new
    {
        Text = a.TextContent.Trim(),
        Href = a.GetAttribute("href")
    })
    .ToList();
Console.WriteLine($"Links found: {links.Count}");

// Extract product data (example)
var products = document.QuerySelectorAll(".product-card")
    .Select(card => new
    {
        Name = card.QuerySelector(".product-name")?.TextContent.Trim(),
        Price = card.QuerySelector(".product-price")?.TextContent.Trim(),
        Url = card.QuerySelector("a")?.GetAttribute("href"),
    })
    .ToList();
Console.WriteLine($"Products: {products.Count}");

// Extract table data
var tableRows = document.QuerySelectorAll("table tbody tr")
    .Select(row => row.QuerySelectorAll("td")
        .Select(cell => cell.TextContent.Trim())
        .ToArray())
    .Where(cells => cells.Length > 0)
    .ToList();
Console.WriteLine($"Table rows: {tableRows.Count}");

Complete Example: Scrape and Parse

Here's a complete program that scrapes a page and extracts structured data.

// Program.cs
using System.Net.Http.Json;
using System.Text.Json;
using AngleSharp.Html.Parser;

var apiKey = "YOUR_API_KEY";

using var client = new HttpClient { Timeout = TimeSpan.FromSeconds(60) };
client.DefaultRequestHeaders.Add("X-API-Key", apiKey);

var scraped = await ScrapeAndParse(client, "https://store.example.com/products");
Console.WriteLine(JsonSerializer.Serialize(scraped, new JsonSerializerOptions
{
    WriteIndented = true
}));

async Task<object> ScrapeAndParse(HttpClient http, string url)
{
    // Scrape the page
    var request = new
    {
        url,
        mode = "auto",
        waitForSelector = ".product-card"
    };

    var response = await http.PostAsJsonAsync("https://api.fastwebscraper.com", request);
    response.EnsureSuccessStatusCode();

    var result = await response.Content.ReadFromJsonAsync<JsonElement>();
    var html = result.GetProperty("data").GetProperty("html").GetString()!;

    // Parse the HTML
    var parser = new HtmlParser();
    var document = await parser.ParseDocumentAsync(html);

    var products = document.QuerySelectorAll(".product-card")
        .Select(card => new
        {
            Name = card.QuerySelector(".product-name")?.TextContent.Trim(),
            Price = card.QuerySelector(".price")?.TextContent.Trim(),
            Image = card.QuerySelector("img")?.GetAttribute("src"),
            Link = card.QuerySelector("a")?.GetAttribute("href"),
        })
        .ToList();

    return new
    {
        Url = url,
        ScrapedAt = DateTime.UtcNow.ToString("o"),
        Products = products
    };
}

Error Handling

Always handle errors and implement retries for production use.

using System.Net.Http.Json;
using System.Text.Json;

async Task<JsonElement> ScrapeWithRetry(
    HttpClient client, string url, int retries = 3)
{
    for (int attempt = 1; attempt <= retries; attempt++)
    {
        try
        {
            var request = new { url, mode = "auto" };
            var response = await client.PostAsJsonAsync(
                "https://api.fastwebscraper.com", request);

            if (response.StatusCode == System.Net.HttpStatusCode.TooManyRequests)
            {
                // Rate limited — wait and retry
                var delay = (int)Math.Pow(2, attempt) * 1000;
                Console.WriteLine($"Rate limited. Waiting {delay}ms...");
                await Task.Delay(delay);
                continue;
            }

            response.EnsureSuccessStatusCode();
            return await response.Content.ReadFromJsonAsync<JsonElement>();
        }
        catch (Exception ex)
        {
            if (attempt == retries) throw;
            var delay = (int)Math.Pow(2, attempt) * 1000;
            Console.WriteLine($"Attempt {attempt} failed: {ex.Message}. Retrying in {delay}ms...");
            await Task.Delay(delay);
        }
    }

    throw new Exception($"Failed after {retries} retries");
}

Concurrent Scraping (Advanced)

For scraping multiple URLs concurrently, use Task.WhenAll with a semaphore to limit concurrency.

using System.Net.Http.Json;
using System.Text.Json;

using var client = new HttpClient();
client.DefaultRequestHeaders.Add("X-API-Key", "YOUR_API_KEY");

var urls = new[]
{
    "https://example.com/page/1",
    "https://example.com/page/2",
    "https://example.com/page/3",
    "https://example.com/page/4",
    "https://example.com/page/5",
};

// Limit to 3 concurrent requests
var semaphore = new SemaphoreSlim(3);

var tasks = urls.Select(async url =>
{
    await semaphore.WaitAsync();
    try
    {
        var request = new { url, mode = "auto" };
        var response = await client.PostAsJsonAsync("https://api.fastwebscraper.com", request);
        var result = await response.Content.ReadFromJsonAsync<JsonElement>();
        var jobId = result.GetProperty("data").GetProperty("jobId").GetString();
        Console.WriteLine($"Queued {url} -> Job {jobId}");
        return new { Url = url, JobId = jobId };
    }
    finally
    {
        semaphore.Release();
    }
});

var results = await Task.WhenAll(tasks);
Console.WriteLine($"Submitted {results.Length} jobs");

Next Steps

API Reference — all endpoints, parameters, and response schemas
Async vs Sync Guide — when to use each scraping mode
Error Handling Guide — production-ready retry patterns
Use Cases — industry-specific scraping examples