private bool UserExistsInLdapDirectory(LdapSettings ldapSettings, LoginInfo loginInfo)
        {
            var userName = loginInfo.UserName != null?loginInfo.UserName.Trim() : loginInfo.Login;

            var filter = I18NHelper.FormatInvariant("(&(objectCategory={0})({1}={2}))", ldapSettings.GetEffectiveUserObjectCategoryAttribute(), ldapSettings.GetEffectiveAccountNameAttribute(), LdapHelper.EscapeLdapSearchFilter(userName));

            try
            {
                var found = _authenticator.SearchLdap(ldapSettings, filter);

                if (found)
                {
                    return(true);
                }

                _log.LogInformation(LogSourceLdap, I18NHelper.FormatInvariant("User '{0}' is not found in LDAP directory {1}", userName, ldapSettings.LdapAuthenticationUrl));

                return(false);
            }
            catch (Exception ex)
            {
                _log.LogInformation(LogSourceLdap, I18NHelper.FormatInvariant("Error while searching a user in LDAP directory {0}", ldapSettings.LdapAuthenticationUrl));
                _log.LogError(LogSourceLdap, ex);

                return(false);
            }
        }