Recaptcha.Verify.Net

Library for verifying Google reCAPTCHA v2/v3 response token for ASP.NET Core. The project targets .NET Core 3.1.

Installation

Package can be installed using Visual Studio UI (Tools > NuGet Package Manager > Manage NuGet Packages for Solution and search for "Recaptcha.Verify.Net").

Also latest version of package can be installed using Package Manager Console:

PM> Install-Package Recaptcha.Verify.Net

Using reCAPTCHA verification

1. Add secret key in appsettings.json file

{
  "Recaptcha": {
    "SecretKey": "<recaptcha secret key>"
  }
}

2. Configure service in Startup.cs

public void ConfigureServices(IServiceCollection services)
{
    services.ConfigureRecaptcha(Configuration.GetSection("Recaptcha"));
    //...
}

3. Use service in controller to verify captcha answer

[ApiController]
[Route("api/[controller]")]
public class LoginController : Controller
{
    private readonly ILogger _logger;
    private readonly IRecaptchaService _recaptchaService;

    public LoginController(ILoggerFactory loggerFactory, IRecaptchaService recaptchaService)
    {
        _logger = loggerFactory.CreateLogger<LoginController>();
        _recaptchaService = recaptchaService;
    }

    [HttpPost]
    public async Task<IActionResult> Login([FromBody] Credentials credentials, CancellationToken cancellationToken)
    {
        var response = await _recaptchaService.VerifyAsync(
            new VerifyRequest()
            {
                Response = credentials.RecaptchaToken
            },
            cancellationToken);

        if (!response.Success)
        {
            _logger.LogError($"Recaptcha error: {JsonConvert.SerializeObject(response.ErrorCodes)}");
            return BadRequest();
        }

        // Process login

        return Ok();
    }
}

Examples

Examples could be found in library repository:

• Recaptcha.Verify.Net.ConsoleApp (.NET Core 3.1)
• Recaptcha.Verify.Net.AspNetCoreAngular (ASP.NET Core 3.1 + Angular)