获得所有的域用户列表

/// <summary>
        /// List all User.
        /// </summary>
        private void ListUser(ComboBox cb)
        {
            DirectoryEntry localMachine = new DirectoryEntry("WinNT://" + Environment.MachineName);
            DirectoryEntry admGroup = localMachine.Children.Find("administrators", "group");
            object members = admGroup.Invoke("members", null);
            foreach (object groupMember in (System.Collections.IEnumerable)members)
            {
                DirectoryEntry member = new DirectoryEntry(groupMember);
                cb.Items.Add(member.Name);
            }
            cb.SelectedIndex = 0;
        }