获得网上邻居里计算机和他们的ip地址

using System;
using System.Net;
using System.DirectoryServices;

public void ShowComputers()
        {
            DirectoryEntry root = new DirectoryEntry("WinNT:");
            DirectoryEntries domains = root.Children;
            domains.SchemaFilter.Add("domain");
            foreach(DirectoryEntry domain in domains)
            {
                string str = "";
                str = domain.Name;
                listBox1.Items.Add("域名：" + str);
                DirectoryEntries computers = domain.Children;
                computers.SchemaFilter.Add("computer");
                foreach(DirectoryEntry computer in computers)
                {
                    str = "";
                    str += " " + computer.Name;
                    try
                    {
                        IPHostEntry  ips = Dns.GetHostByName(computer.Name);
                        foreach(IPAddress ip in ips.AddressList)
                        {
                            str += "  " + ip;
                        }
                    }
                    catch{
                        Console.WriteLine(computer.Name);
                    }
                    DirectoryEntries  users = computer.Children;
                    listBox1.Items.Add(str);
                }
            }
        }