13

 public static string GetCertRequestTemplate(string context)
        {
            var binaryData = CertificateHelper.GetBinaryDataFromStringContext(context);

            var certRequest = new Pkcs10CertificationRequest(binaryData);

            var certRequestInfo = certRequest.GetCertificationRequestInfo();

            IEnumerable<DerSequence> extensionSequence = certRequestInfo.Attributes.OfType<DerSequence>().Where(o => o.OfType<DerObjectIdentifier>().Any());

            foreach (var seq in extensionSequence)
            {
                DerSet extensionSet = seq.OfType<DerSet>().FirstOrDefault();

                if (extensionSet.OfType<DerSequence>().Any())
                {
                    DerOctetString str = GetAsn1ObjectRecursive<DerOctetString>(extensionSet.OfType<DerSequence>().First(), "1.3.6.1.4.1.311.21.7");

                    if (str != null) return str.Parser.ToString();
                }
            }

            return "";
        }

        static T GetAsn1ObjectRecursive<T>(DerSequence sequence, String id) where T : Asn1Object
        {
            if (sequence.OfType<DerObjectIdentifier>().Any(o => o.Id == id))
            {
                return sequence.OfType<T>().First();
            }

            foreach (DerSequence subSequence in sequence.OfType<DerSequence>())
            {
                T value = GetAsn1ObjectRecursive<T>(subSequence, id);
                if (value != default(T))
                {
                    return value;
                }
            }

            return default(T);
        }