LdapDirectoryIdentifier ldap_id = new LdapDirectoryIdentifier(
                                            host,
                                            Int32.Parse(port),
                                            true,
                                            false);
LdapConnection con = new LdapConnection(ldap_id);

con.AuthType = AuthType.Kerberos;
con.SessionOptions.Sealing = true;
con.SessionOptions.Signing = true;
con.SessionOptions.ProtocolVersion = 3;

con.Bind();

LdapDirectoryIdentifier ldapIdentifier = new LdapDirectoryIdentifier(
                                            host,
                                            Int32.Parse(port),
                                            true,
                                            false);
NetworkCredential credential = new NetworkCredential(username, password);
LdapConnection con = new LdapConnection(ldapIdentifier, credential, AuthType.Kerberos);
con.SessionOptions.Sealing = true;
con.SessionOptions.Signing = true;
con.SessionOptions.ProtocolVersion = 3;
con.Bind();

var networkCredential = new NetworkCredential(connectionAccountName, connectionAccountPassword);
LdapDirectoryIdentifier ldapDirectoryIdentifier = null;

switch (connectionType)
{
    case LDAPConnectionType.SSL:
                ldapDirectoryIdentifier = new LdapDirectoryIdentifier(ldapServerName, Convert.ToInt16(LDAPPorts.SSL));
                ldapConnection = new LdapConnection(ldapDirectoryIdentifier, networkCredential, authType);
                ldapConnection.SessionOptions.ProtocolVersion = 3;
                ldapConnection.SessionOptions.VerifyServerCertificate = new VerifyServerCertificateCallback(ServerCallback);
                ldapConnection.SessionOptions.SecureSocketLayer = true;

                break;

    case LDAPConnectionType.TLS:
                ldapDirectoryIdentifier = new LdapDirectoryIdentifier(ldapServerName, Convert.ToInt16(LDAPPorts.Default));
                ldapConnection = new LdapConnection(ldapDirectoryIdentifier, networkCredential, authType);
                ldapConnection.SessionOptions.VerifyServerCertificate = new VerifyServerCertificateCallback(ServerCallback);
                ldapConnection.SessionOptions.StartTransportLayerSecurity(null);

                break;

    default:
                ldapDirectoryIdentifier = new LdapDirectoryIdentifier(ldapServerName, Convert.ToInt16(LDAPPorts.Default));
                ldapConnection = new LdapConnection(ldapDirectoryIdentifier, networkCredential, authType);

                break;
}

ldapConnection.Bind();