How to query openldap for public encryption certificate and get expiry date from usercertificate; binary

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C#

I am trying to create "certificate explorer" that will query our openldap server by "cn=userinfo" and return the public encryption certificate Name, Email and Validto date.

I am able to return the CN and mail information,

I am unable to get the usercertificate;binary information and parse out the attributes.

What I have tried:

try
            {
                
                // Create the new LDAP connection
                Console.WriteLine("Attempting LDAP connection.");
                LdapDirectoryIdentifier ldi = new LdapDirectoryIdentifier("server.addr.org", 389);
                System.DirectoryServices.Protocols.LdapConnection ldapConnection =
                    new System.DirectoryServices.Protocols.LdapConnection(ldi);
                Console.WriteLine("LdapConnection is created successfully.");
                //ldapConnection.AuthType = AuthType.Basic;
                ldapConnection.AuthType = AuthType.Anonymous;
                ldapConnection.SessionOptions.ProtocolVersion = 3;
                //NetworkCredential nc = new NetworkCredential("uid=testa,ou=people,dc=ghashd,dc=servebeer,dc=com",
                //  "zaq12wsx"); //password
                NetworkCredential nc = new NetworkCredential();
                ldapConnection.Bind(nc);
                Console.WriteLine("LdapConnection anonymous authentication successfull");
                
                System.DirectoryServices.Protocols.SearchRequest srch =
                //new System.DirectoryServices.Protocols.SearchRequest(dn, filter, System.DirectoryServices.Protocols.SearchScope.Subtree, atrList);
                new System.DirectoryServices.Protocols.SearchRequest();
                //srch.Filter = "(cn=" + searchString + ")";
                //srch.Filter = "(cn=*me*)";
                srch.Filter = "(cn=" + searchString + ")";
                srch.Scope = System.DirectoryServices.Protocols.SearchScope.Subtree;
                srch.DistinguishedName = "o=u.s. government, c=us";

                System.DirectoryServices.Protocols.SearchResponse response = (System.DirectoryServices.Protocols.SearchResponse)ldapConnection.SendRequest(srch);

                Console.WriteLine("Ldap search request sent");

                Console.WriteLine("Number of results: " + response.Entries.Count);

                //System.DirectoryServices.Protocols.SearchResultEntry entry = response.Entries[0];

                foreach (System.DirectoryServices.Protocols.SearchResultEntry entry in response.Entries)
                {

                    if (m_stop)
                    {
                        ldapConnection.Dispose();
                        break;
                    }



                    DirectoryAttribute cn = entry.Attributes["cn"];
                    DirectoryAttribute mailattr = entry.Attributes["mail"];
                    DirectoryAttribute binaryAttr = entry.Attributes["usercertificate;binary"];
                    
                    //Console.WriteLine(" BA Count: " + binaryAttr.Count);



                    if (entry.Attributes["mail"] != null)
                    {
                        Console.WriteLine("Mail count: " + mailattr.Count);
                    }
                        //Console.WriteLine("DN: " + entry.DistinguishedName);
                    //Console.WriteLine("Attr count: " + entry.Attributes.Count);
                    string email = null;

                    string name = Convert.ToString(cn[0]);

                    if (entry.Attributes["mail"] != null)
                    {
                        email = Convert.ToString(mailattr[0]);
                    }
                    //Console.WriteLine("Name: " + cn[0]);
                    //Console.WriteLine("Email: " + mailattr[0]);
                    Console.WriteLine("Name: " + name);

                    
                    Console.WriteLine("Email: " + email);
                    //Console.WriteLine("Binary: " + sb);


                    if (email != null)
                    {
                        Console.WriteLine(mailattr.Name + "=" + email);
                    }

                    else
                    {
                        Console.WriteLine("No Email Attribute assigned");

                    }

                    // We have found a matching FileSystemInfo, so let's raise an event:
                    if (FoundInfo != null && email != null)
                    {
                        FoundInfo(new FoundInfoEventArgs(name, email));
                    }
                    else if (FoundInfo != null)
                    {
                        FoundInfo(new FoundInfoEventArgs(name, "No Email in cert"));
                    }