Whois 4.0.0-beta.1

.NET WHOIS Lookup and Parser

Query and parse WHOIS domain registration information with this library for .NET Standard 2.0, .NET 8, and .NET 10.

// Create a WhoisLookup instance
var lookup = new WhoisLookup();

// Query github.com
var response = await lookup.Lookup("github.com");

// Output the response
Console.WriteLine(response.Content);

// Domain Name: github.com
// Registry Domain ID: 1264983250_DOMAIN_COM-VRSN
// Registrar WHOIS Server: whois.markmonitor.com
// Registrar URL: http://www.markmonitor.com
// ...

Parsing

WHOIS data is parsed into objects using extensible Tokenizer templates.

// Query github.com
var response = await lookup.Lookup("github.com");

// Convert the response to JSON
var json = JsonSerializer.Serialize(response, new JsonSerializerOptions { WriteIndented = true });

// Output the json 
Console.WriteLine(json);

// {
//   "ContentLength": 3730,
//   "Status": 1,
//   "DomainName": {
//     "IsPunyCode": false,
//     "IsTld": false,
//     "Tld": "com",
//     "Value": "github.com"
//   },
//   "RegistryDomainId": "1264983250_DOMAIN_COM-VRSN",
//   "DomainStatus": [
//     "clientUpdateProhibited",
//     "clientTransferProhibited",
//     "clientDeleteProhibited"
//   ],
//   "Registered": "2007-10-09T18:20:50Z",
//   "Updated": "2020-09-08T09:18:27Z",
//   "Expiration": "2022-10-09T07:00:00Z",
// ...

CancellationToken Support

All async methods accept a CancellationToken for cooperative cancellation:

using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));

var response = await lookup.Lookup("github.com", cts.Token);

Configuration

Configure the lookup per-instance using the options constructor parameter:

var lookup = new WhoisLookup(new WhoisOptions
{
    TimeoutSeconds = 30,
    FollowReferrer = true
});

Dependency Injection

The library integrates with Microsoft.Extensions.DependencyInjection via the AddWhois() extension method:

// In Startup/Program.cs — configure with a lambda
services.AddWhois(options =>
{
    options.TimeoutSeconds = 30;
    options.FollowReferrer = true;
});

// Or bind from IConfiguration
services.AddWhois(configuration.GetSection("Whois"));

Inject IWhoisLookup into your services:

public class MyService(IWhoisLookup whoisLookup)
{
    public async Task<WhoisResponse> CheckDomain(string domain, CancellationToken ct)
        => await whoisLookup.Lookup(domain, ct);
}

Logging

The library uses Microsoft.Extensions.Logging. When registered via DI, an ILogger<WhoisLookup> is automatically injected. For standalone use, pass a logger factory explicitly:

using var loggerFactory = LoggerFactory.Create(builder => builder.AddConsole());

var lookup = new WhoisLookup(logger: loggerFactory.CreateLogger<WhoisLookup>());

Extending

Parsing More Data

If a registrar's WHOIS data isn't being parsed correctly, you can simply add a new template:

var lookup = new WhoisLookup();

// Clear the embedded templates (not recommended)
lookup.Parser.ClearTemplates();

// Add a custom WHOIS response parsing template
lookup.Parser.AddTemplate("Domain: { DomainName$ }", "Simple Pattern");

See the existing patterns and Tokenizer documentation for information about creating patterns. You can also add validation and transformation functions to your patterns.

Networking

The library communicates via an ITcpReader interface. The default implementation will talk directly to a WHOIS server over port 43. You can change this behaviour by creating a new ITcpReader implementation and passing it to the constructor:

// Create a custom ITcpReader implementation
class MyCustomTcpReader : ITcpReader
{
    private readonly ITcpReader _inner = new TcpReader();

    public Task<string> Read(string url, int port, string command, Encoding encoding, int timeoutSeconds, CancellationToken cancellationToken)
    {
        Console.WriteLine($"Reading from URL: {url}");

        return _inner.Read(url, port, command, encoding, timeoutSeconds, cancellationToken);
    }
}

// Create a WhoisLookup instance with the custom reader
var lookup = new WhoisLookup(tcpReader: new MyCustomTcpReader());

// Lookups will now use the custom TcpReader
var response = await lookup.Lookup("github.com");

Installation

You can install the library via the NuGet GUI or by entering the following command into the Package Manager Console:

Install-Package Whois -Version 4.0.0

The source code is available on Github and can be downloaded and compiled.

Further Reading

Further details about how the library works can be found on this blog post.