/// <summary>
 /// Remove ADUser from group
 /// </summary>
 /// <param name="userlogin"></param>
 /// <param name="groupName"></param>
 /// <returns></returns>
 public bool RemoveUserToGroup(string userlogin, string groupName)
 {
     try
     {
         _directoryEntry = null;
         ADManager admanager = new ADManager("xxx", ADConfig.LDAPUser, ADConfig.LDAPPassword);
         admanager.RemoveUserFromGroup(userlogin, groupName);
         return true;
     }
     catch (Exception ex)
     {
         return false;
     }
 }