CheckSslCertificate.cs

        public static void CheckSslCertificate(string url)
        {
            try
            {
                // 建立 HttpClientHandler 並攔截憑證驗證
                using var handler = new HttpClientHandler();
                handler.ServerCertificateCustomValidationCallback = (request, cert, chain, errors) =>
                {
                    var x509 = new X509Certificate2(cert);

                    Console.WriteLine("=== SSL 憑證資訊 ===");
                    Console.WriteLine("網站:" + url);
                    Console.WriteLine("主題:" + x509.Subject);
                    Console.WriteLine("頒發者:" + x509.Issuer);
                    Console.WriteLine("生效日:" + x509.NotBefore);
                    Console.WriteLine("到期日:" + x509.NotAfter);
                    Console.WriteLine("是否過期:" + (DateTime.Now > x509.NotAfter ? "是" : "否"));
                    Console.WriteLine("剩餘天數:" + (x509.NotAfter - DateTime.Now).TotalDays + " 天");
                    Console.WriteLine("====================");

                    return true;
                };

                using var client = new HttpClient(handler);

                // 模擬瀏覽器 User-Agent，避免被 CDN 阻擋
                client.DefaultRequestHeaders.Add(
                    "User-Agent",
                    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 " +
                    "(KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36"
                );

              
                var task = client.GetAsync(url);
                task.Wait();
                var response = task.Result;

                Console.WriteLine("HTTP 狀態碼: " + (int)response.StatusCode);
            }
            catch (Exception ex)
            {
                Console.WriteLine("發生錯誤：" + ex.Message);
            }
        }
        
        

gistfile1.txt

            CheckSslCertificate("https://www.google.com");

            CheckSslCertificate("https://blog.no2don.com");

            //沒有SSL
            CheckSslCertificate("https://no2don.com");