C#获取SMTP-Server的SSL证书过期日期作为从服务器证书验证回调的返回值

Question

目前，我有以下代码来获取SMTP服务器的到期日期：

namespace SMTPCert
{
    public class SMTPCert
    {
        public static void GetSMTPCert(string ServerName)
        {
            ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(RemoteServerCertificateValidationCallback);
            using (System.Net.Mail.SmtpClient S = new System.Net.Mail.SmtpClient(ServerName))
            {
                S.EnableSsl = true;
                using (System.Net.Mail.MailMessage M = new System.Net.Mail.MailMessage("[e-mail]", "[e-mail]", "Test", "Test"))
                {
                    try
                    {
                        S.Send(M);
                    }
                    catch (Exception)
                    {
                        return;
                    }
                }
            }
        }
}
我的问题是我想将GetSMTPCert方法从false更改为字符串，以便我可以将证书到期日期返回给我的主方法。但目前我只能在Remote teServerCerateValidationCallback方法中获取到期日期，无法从那里返回。有没有可能的方法来获取我的GetSMTPCert方法的证书到期日期，然后将其返回给我的主方法？
我们也欢迎您提供有关获取SMTP服务器SSL证书到期日期的其他方法的建议。
                

Answer 1

好的，我通过将字符串“CertificateDaysLeft”类型的公共静态字段添加到SMTPCert类中解决了这个问题。

namespace SMTPCert
{
    public static string CertificateDaysLeft;

    public static string GetSMTPCert(string ServerName)
    {
        ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(RemoteServerCertificateValidationCallback);
        using (System.Net.Mail.SmtpClient S = new System.Net.Mail.SmtpClient(ServerName))
        {
            S.EnableSsl = true;
            using (System.Net.Mail.MailMessage M = new System.Net.Mail.MailMessage("[e-mail]", "[e-mail]", "Test", "Test"))
            {
                try
                {
                    S.Send(M);
                    string daysLeft = CertificateDaysLeft;
                    return daysLeft;
                }
                catch (Exception)
                {
                    string daysLeft = CertificateDaysLeft;
                    return daysLeft;
                }
            }
        }
    }

    private static bool RemoteServerCertificateValidationCallback(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
    {
        DateTime ExpirDate = Convert.ToDateTime(certificate.GetExpirationDateString());
        string DaysLeft = Convert.ToString((ExpirDate - DateTime.Today).Days);
        CertificateDaysLeft = DaysLeft;
        Console.WriteLine(certificate);
        return true;
    }
}

}

我想我觉得有点太复杂了。