iTextSharp.text.pdf.PdfPKCS7.VerifyCertificate C# (CSharp) Метод

        public static String VerifyCertificate(X509Certificate cert, object[] crls, DateTime calendar) {
            try {
                if (!cert.IsValid(calendar))
                    return "The certificate has expired or is not yet valid";
            }
            catch (Exception e) {
                return e.ToString();
            }
            return null;
        }