Certificate pinning example using C#

Program.cs

using System;
using System.IO;
using System.Net;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;
using System.Text.Json;

namespace CertificatePinningTutorial
{
    internal class Program
    {
        private readonly string _domain;

        private Program(string domain)
        {
            _domain = domain;
        }

        private String GetSha1ThumbprintFromApi()
        {
            ServicePointManager.ServerCertificateValidationCallback = null;
            var requestUriString = $"https://api.cert.ist/{_domain}";
            WebRequest request = WebRequest.Create(requestUriString);
            HttpWebResponse response = (HttpWebResponse) request.GetResponse();
            StreamReader reader = new StreamReader(response.GetResponseStream()!);
            CertIstApi certIstApi = JsonSerializer.Deserialize<CertIstApi>(reader.ReadToEnd());
            return certIstApi.certificate.hashes.sha1;
        }

        private void ValidateDomain()
        {
            try
            {
                WebRequest.DefaultWebProxy = null;
                ServicePointManager.ServerCertificateValidationCallback = PinPublicKey;
                WebRequest wr = WebRequest.Create($"https://{_domain}");
                wr.GetResponse();
            }
            catch (WebException)
            {
                Environment.Exit(1);
            }
        }

        // ReSharper disable once UnusedParameter.Global
        public static void Main(string[] _)
        {
            new Program("wordpress.com").ValidateDomain();
            new Program("urip.com").ValidateDomain();
            new Program("xkcd.com").ValidateDomain();
            new Program("cert.ist").ValidateDomain();
        }

        private bool PinPublicKey(object sender, X509Certificate certificate, X509Chain chain,
            SslPolicyErrors sslPolicyErrors)
        {
            var keyDerFromApis = GetSha1ThumbprintFromApi();
            if (null == certificate)
            {
                return false;
            }

            var cert = new X509Certificate2(certificate);
            var isPinnedThumbprintValid =
                cert.Thumbprint != null && cert.Thumbprint.ToLower().Equals(keyDerFromApis.ToLower());
            Console.WriteLine($"{_domain} certificate sha1 from api: {keyDerFromApis}, is valid: {isPinnedThumbprintValid}");
            return isPinnedThumbprintValid;
        }
    }
}

// this is the minimum we can deserialize to pin the certificate
// ReSharper disable once ClassNeverInstantiated.Global
public class CertIstApiKeyStats
{
    // ReSharper disable once UnusedAutoPropertyAccessor.Global
    // ReSharper disable once InconsistentNaming
    public CertIstApiHashes hashes { get; set; }
}

// ReSharper disable once ClassNeverInstantiated.Global
public class CertIstApi
{
    // ReSharper disable once UnusedAutoPropertyAccessor.Global
    // ReSharper disable once InconsistentNaming
    public CertIstApiKeyStats certificate { get; set; }
}


// ReSharper disable once ClassNeverInstantiated.Global
public class CertIstApiHashes
{
    // ReSharper disable once UnusedAutoPropertyAccessor.Global
    // ReSharper disable once InconsistentNaming
    public string sha1 { get; set; }
}