pas/Api/Helpers/ReCapthchaAssessment.cs

using System;
using Google.Api.Gax.ResourceNames;
using Google.Cloud.RecaptchaEnterprise.V1;

namespace Api.Helpers
{
    public static class ReCaptchaAssessment
    {
        // Checks the supplied token with Recaptcha Enterprise and returns true if valid.
        // Outputs a short reason when false (invalid reason or exception message).
        public static bool CheckToken(string token, out string reason, string projectId = "webserverfarm", string recaptchaKey = "6Lf6df0rAAAAAMXcAx1umneXl1QJo9rTrflpWCvB")
        {
            reason = string.Empty;

            if (string.IsNullOrWhiteSpace(token))
            {
                reason = "empty-token";
                return false;
            }

            try
            {
                var client = RecaptchaEnterpriseServiceClient.Create();

                var request = new CreateAssessmentRequest
                {
                    Parent = $"projects/{projectId}",
                    Assessment = new Assessment
                    {
                        Event = new Event
                        {
                            SiteKey = recaptchaKey,
                            Token = token
                        }
                    }
                };

                var response = client.CreateAssessment(request);

                if (response?.TokenProperties == null)
                {
                    reason = "missing-token-properties";
                    return false;
                }

                if (!response.TokenProperties.Valid)
                {
                    reason = response.TokenProperties.InvalidReason.ToString();
                    return false;
                }

                reason = "valid";
                return true;
            }
            catch (Exception ex)
            {
                reason = ex.Message;
                return false;
            }
        }
    }
}