Curl DotNet: Bringing Curl Superpowers to the .NET Runtime

Key Features

• Zero Translation: Paste curl HTTPS commands directly into your C# source.

• Cross-Platform: Full support for Windows, Linux, MacOS, and more.

• Type Safety: Option to use a fluent builder for dependency injection scenarios.

• Observability: Built-in support to emit structured events for logging.

The String API: Paste and Go Curl Commands

This method is perfect for health checks, support agents, or rapid prototyping. You simply pass the curl command as a string.

using CurlDotNet;

// Simply paste the command string
var response = await Curl.ExecuteAsync("curl https://api.github.com/users/octocat");

// Access the data
Console.WriteLine(response.Body);

using CurlDotNet;

// Simply paste the command string
var response = await Curl.ExecuteAsync("curl https://api.github.com/users/octocat");

// Access the data
Console.WriteLine(response.Body);

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Using the Fluent Builder with Environment Variables

For production applications where you need to handle sensitive data via environment variables, or require cleaner architecture, the fluent builder is ideal. You can specify a string name for headers or set a file path explicitly.

var response = await Curl.GetAsync("https://api.example.com/data")
    .WithHeader("Authorization", "Bearer " + Environment.GetEnvironmentVariable("API_KEY"))
    .WithTimeout(TimeSpan.FromSeconds(30))
    .ExecuteAsync();

var response = await Curl.GetAsync("https://api.example.com/data")
    .WithHeader("Authorization", "Bearer " + Environment.GetEnvironmentVariable("API_KEY"))
    .WithTimeout(TimeSpan.FromSeconds(30))
    .ExecuteAsync();

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Example 1: Secure PDF Download and Editing with IronPDF

IronPDF is the industry standard for generating pixel-perfect PDFs in .NET. Unlike other libraries that struggle with modern web standards, IronPDF renders HTML, CSS, and JavaScript exactly as a Chrome browser would. It is built to be a complete solution: you can generate new documents from HTML strings or files, edit existing PDFs, merge documents, and apply security features like watermarking and encryption without needing external dependencies or Adobe Acrobat installed on the server.

Imagine you need to download a generated invoice from a legacy internal system that requires complex curl flags (like ignoring SSL errors or specific header permutations), and then watermark it using IronPDF.

Translating that request to HttpClient might take hours of debugging. With CurlDotNet, you paste the command, get the bytes, and hand them to IronPDF.

using CurlDotNet;
using IronPdf;

// 1. Use CurlDotNet to handle the complex transport
// We use -k to allow insecure SSL (common in legacy internal apps)
var curlCommand = "curl -k https://internal-billing.local/invoice/1234 -H 'X-Dept: Sales'";
var response = await Curl.ExecuteAsync(curlCommand);

if (response.IsSuccess)
{
    // 2. Pass the raw bytes directly to IronPDF
    // IronPDF renders the PDF from the downloaded data
    var pdfDocument = PdfDocument.FromPdf(response.BodyBytes);

    // 3. Apply a watermark and save
    pdfDocument.ApplyWatermark("CONFIDENTIAL", 30, VerticalAlignment.Middle, HorizontalAlignment.Center);
    pdfDocument.SaveAs("Processed_Invoice.pdf");

    Console.WriteLine("Invoice downloaded and secured via IronPDF.");
}

using CurlDotNet;
using IronPdf;

// 1. Use CurlDotNet to handle the complex transport
// We use -k to allow insecure SSL (common in legacy internal apps)
var curlCommand = "curl -k https://internal-billing.local/invoice/1234 -H 'X-Dept: Sales'";
var response = await Curl.ExecuteAsync(curlCommand);

if (response.IsSuccess)
{
    // 2. Pass the raw bytes directly to IronPDF
    // IronPDF renders the PDF from the downloaded data
    var pdfDocument = PdfDocument.FromPdf(response.BodyBytes);

    // 3. Apply a watermark and save
    pdfDocument.ApplyWatermark("CONFIDENTIAL", 30, VerticalAlignment.Middle, HorizontalAlignment.Center);
    pdfDocument.SaveAs("Processed_Invoice.pdf");

    Console.WriteLine("Invoice downloaded and secured via IronPDF.");
}

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Console Confirmation

PDF Output

Example 2: Scraping and OCR with IronOCR

IronOCR is an advanced optical character recognition library powered by the Tesseract 5 engine, fine-tuned specifically for C# and .NET. It supports over 127 languages and excels at reading text from imperfect sources—think low-resolution scans, rotated images, or noisy backgrounds. Its "Computer Vision" capabilities allow it to detect text regions automatically, and it can output data not just as plain strings, but as structured content (barcodes, paragraphs, lines, and characters) for deep analysis.

Sometimes you need to extract data from an image hosted on a server that blocks standard .NET scrapers. You can use CurlDotNet to mimic a standard browser user agent effortlessly, then use IronOCR to read the text.

using CurlDotNet;
using IronOcr;

// 1. Fetch the image using a specific browser User-Agent to bypass blocks
var imgResponse = await Curl.GetAsync("https://site.com/protected-captcha.png")
    .WithUserAgent("Mozilla/5.0 (Windows NT 10.0; Win64; x64)")
    .ExecuteAsync();

// 2. Use IronOCR to read text from the file bytes
var ocr = new IronTesseract();
using (var input = new OcrInput())
{
    input.AddImage(imgResponse.BodyBytes);
    var result = ocr.Read(input);

    // 3. Output the extracted string value
    Console.WriteLine($"OCR Result: {result.Text}");
}

using CurlDotNet;
using IronOcr;

// 1. Fetch the image using a specific browser User-Agent to bypass blocks
var imgResponse = await Curl.GetAsync("https://site.com/protected-captcha.png")
    .WithUserAgent("Mozilla/5.0 (Windows NT 10.0; Win64; x64)")
    .ExecuteAsync();

// 2. Use IronOCR to read text from the file bytes
var ocr = new IronTesseract();
using (var input = new OcrInput())
{
    input.AddImage(imgResponse.BodyBytes);
    var result = ocr.Read(input);

    // 3. Output the extracted string value
    Console.WriteLine($"OCR Result: {result.Text}");
}

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OCR Example Output

Example 3: Managing Inventory with IronBarcode

using CurlDotNet;
using IronBarCode;

class Program
{
    private static readonly HttpClient client = new HttpClient();
    public static async Task Main(string[] args)
    {

        // 1. Define the URL 
        string url = "https://barcodeapi.org/api/128/Shipping-Label-Test-123";

        try
        {
            // Add the session cookie to the request headers
            client.DefaultRequestHeaders.Add("Cookie", "session_id=xyz123");

            // 2. Download the image data as a Byte Array (Preserves binary integrity)
            byte[] imageBytes = await client.GetByteArrayAsync(url);

            Console.WriteLine($"Downloaded {imageBytes.Length} bytes.");

            // 3. Read the barcode directly from the byte array
            var result = BarcodeReader.Read(imageBytes);

            foreach (var barcode in result)
            {
                Console.WriteLine($"Detected Format: {barcode.BarcodeType}");
                Console.WriteLine($"Value: {barcode.Value}");
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error: {ex.Message}");
        }
    }
}

using CurlDotNet;
using IronBarCode;

class Program
{
    private static readonly HttpClient client = new HttpClient();
    public static async Task Main(string[] args)
    {

        // 1. Define the URL 
        string url = "https://barcodeapi.org/api/128/Shipping-Label-Test-123";

        try
        {
            // Add the session cookie to the request headers
            client.DefaultRequestHeaders.Add("Cookie", "session_id=xyz123");

            // 2. Download the image data as a Byte Array (Preserves binary integrity)
            byte[] imageBytes = await client.GetByteArrayAsync(url);

            Console.WriteLine($"Downloaded {imageBytes.Length} bytes.");

            // 3. Read the barcode directly from the byte array
            var result = BarcodeReader.Read(imageBytes);

            foreach (var barcode in result)
            {
                Console.WriteLine($"Detected Format: {barcode.BarcodeType}");
                Console.WriteLine($"Value: {barcode.Value}");
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error: {ex.Message}");
        }
    }
}

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