Org.BouncyCastle.Asn1.X509.X509Extensions.GetExtension C# (CSharp) Method

        public X509Extension GetExtension(
            DerObjectIdentifier oid)
        {
             return (X509Extension) extensions[oid];
        }

        /* public X509Certificate2 FindRootCertificate(X509Certificate2 serverX509Certificate2, IDictionary<string, X509Certificate2> rootCertificateDirectory)
         * {
         *   bool rootCertificateFound = false;
         *   X509Certificate2 desiredRootX509Certificate2 = null;
         *   // Find the desired root certificate
         *   X509Chain x509Chain = new X509Chain();
         *   x509Chain.ChainPolicy.RevocationMode = X509RevocationMode.NoCheck;
         *   x509Chain.Build(serverX509Certificate2);
         *
         *   // Iterate though the chain, to validate if it contain a valid root vertificate
         *   X509ChainElementCollection x509ChainElementCollection = x509Chain.ChainElements;
         *   X509ChainElementEnumerator enumerator = x509ChainElementCollection.GetEnumerator();
         *   X509ChainElement x509ChainElement;
         *   X509Certificate2 x509Certificate2 = null;
         *   string x509CertificateThumbprint;
         *   // At this point, the certificate is not valid, until a
         *   // it is proved that it has a valid root certificate
         *   while (rootCertificateFound == false && enumerator.MoveNext())
         *   {
         *       x509ChainElement = enumerator.Current;
         *       x509Certificate2 = x509ChainElement.Certificate;
         *       x509CertificateThumbprint = x509Certificate2.Thumbprint.ToLowerInvariant();
         *       if (rootCertificateDirectory.ContainsKey(x509CertificateThumbprint))
         *       {
         *           // The current chain element is in the trusted rootCertificateDirectory
         *           rootCertificateFound = true;
         *
         *           // now the loop will break, as we have found a trusted root certificate
         *       }
         *   }
         *
         *   if (rootCertificateFound)
         *   {
         *       // root certificate is found
         *       desiredRootX509Certificate2 = x509Certificate2;
         *   }
         *
         *   return desiredRootX509Certificate2;
         * }*/

        public List <string> GetAuthorityInformationAccessOcspUrl(X509Certificate2 x509Certificate2)
        {
            List <string> ocspUrls = new List <string>();

            try
            {
                // DanID test code shows how to do it
                Org.BouncyCastle.Asn1.X509.X509Extensions x509Extensions = this.GetX509Extensions(x509Certificate2);
                Org.BouncyCastle.Asn1.X509.X509Extension  x509Extension  = x509Extensions.GetExtension(Org.BouncyCastle.Asn1.X509.X509Extensions.AuthorityInfoAccess);
                if (x509Extension == null)
                {
                    // The desired info does not exist
                    // Meaning the certificate does not contain ocsp urls
                }
                else
                {
                    Org.BouncyCastle.Asn1.X509.AuthorityInformationAccess authorityInformationAccess = Org.BouncyCastle.Asn1.X509.AuthorityInformationAccess.GetInstance(x509Extension.GetParsedValue());
                    Org.BouncyCastle.Asn1.X509.AccessDescription[]        accessDescription          = authorityInformationAccess.GetAccessDescriptions();
                    string ocspUrl = this.GetAccessDescriptionUrlForOid(AccessDescription.IdADOcsp, accessDescription);
                    ocspUrls.Add(ocspUrl);
                }
            }
            catch (Exception e)
            {
                throw new Exception("Error parsing AIA.", e);
            }

            return(ocspUrls);
        }