internal static PkixCertPathValidatorResult ProcessAttrCert2(
            PkixCertPath certPath,
            PkixParameters pkixParams)
        {
            PkixCertPathValidator validator = new PkixCertPathValidator();

            try
            {
                return(validator.Validate(certPath, pkixParams));
            }
            catch (PkixCertPathValidatorException e)
            {
                throw new PkixCertPathValidatorException(
                          "Certification path for issuer certificate of attribute certificate could not be validated.",
                          e);
            }
        }
        protected virtual PkixCertPathBuilderResult Build(
            X509Certificate tbvCert,
            PkixBuilderParameters pkixParams,
            IList tbvPath)
        {
            // If tbvCert is readily present in tbvPath, it indicates having run
            // into a cycle in the PKI graph.
            if (tbvPath.Contains(tbvCert))
            {
                return(null);
            }

            // step out, the certificate is not allowed to appear in a certification
            // chain.
            if (pkixParams.GetExcludedCerts().Contains(tbvCert))
            {
                return(null);
            }

            // test if certificate path exceeds maximum length
            if (pkixParams.MaxPathLength != -1)
            {
                if (tbvPath.Count - 1 > pkixParams.MaxPathLength)
                {
                    return(null);
                }
            }

            tbvPath.Add(tbvCert);

//			X509CertificateParser certParser = new X509CertificateParser();
            PkixCertPathBuilderResult builderResult = null;
            PkixCertPathValidator     validator     = new PkixCertPathValidator();

            try
            {
                // check whether the issuer of <tbvCert> is a TrustAnchor
                if (PkixCertPathValidatorUtilities.IsIssuerTrustAnchor(tbvCert, pkixParams.GetTrustAnchors()))
                {
                    // exception message from possibly later tried certification
                    // chains
                    PkixCertPath certPath = null;
                    try
                    {
                        certPath = new PkixCertPath(tbvPath);
                    }
                    catch (Exception e)
                    {
                        throw new Exception(
                                  "Certification path could not be constructed from certificate list.",
                                  e);
                    }

                    PkixCertPathValidatorResult result = null;
                    try
                    {
                        result = (PkixCertPathValidatorResult)validator.Validate(
                            certPath, pkixParams);
                    }
                    catch (Exception e)
                    {
                        throw new Exception(
                                  "Certification path could not be validated.", e);
                    }

                    return(new PkixCertPathBuilderResult(certPath, result.TrustAnchor,
                                                         result.PolicyTree, result.SubjectPublicKey));
                }
                else
                {
                    // add additional X.509 stores from locations in certificate
                    try
                    {
                        PkixCertPathValidatorUtilities.AddAdditionalStoresFromAltNames(
                            tbvCert, pkixParams);
                    }
                    catch (CertificateParsingException e)
                    {
                        throw new Exception(
                                  "No additiontal X.509 stores can be added from certificate locations.",
                                  e);
                    }

                    // try to get the issuer certificate from one of the stores
                    HashSet issuers = new HashSet();
                    try
                    {
                        issuers.AddAll(PkixCertPathValidatorUtilities.FindIssuerCerts(tbvCert, pkixParams));
                    }
                    catch (Exception e)
                    {
                        throw new Exception(
                                  "Cannot find issuer certificate for certificate in certification path.",
                                  e);
                    }

                    if (issuers.IsEmpty)
                    {
                        throw new Exception("No issuer certificate for certificate in certification path found.");
                    }

                    foreach (X509Certificate issuer in issuers)
                    {
                        builderResult = Build(issuer, pkixParams, tbvPath);

                        if (builderResult != null)
                        {
                            break;
                        }
                    }
                }
            }
            catch (Exception e)
            {
                certPathException = e;
            }

            if (builderResult == null)
            {
                tbvPath.Remove(tbvCert);
            }

            return(builderResult);
        }