private void SortUsers(ref List<User> userList)
    {
        if (SortOrder == SortingOrder.Ascending)
        {
            switch (SortExpression)
            {
                case "Role":
                    userList = userList.OrderBy(user => user.Role).ToList();
                    break;
                case "Policy":
                    userList = userList.OrderBy(user => user.Policy).ToList();
                    break;
                default:
                    userList = userList.OrderBy(user => user.Name).ToList();
                    break;
            }
        }
        else
        {
            switch (SortExpression)
            {
                case "Role":
                    userList = userList.OrderByDescending(user => user.Role).ToList();
                    break;
                case "Policy":
                    userList = userList.OrderByDescending(user => user.Policy).ToList();
                    break;
                default:
                    userList = userList.OrderByDescending(user => user.Name).ToList();
                    break;
            }
        }
    }