如何扫描局域网内所有机器的IP？？？

Question

  public string IPList = "";
        private void button4_Click(object sender, EventArgs e)
        {
            String ipPrefix = "192.168.0.";
            for (int i = 2; i <= 255; i++)
            {
                Ping myPing = new Ping();
                string strScanIPAdd = ipPrefix + i.ToString();
                myPing.PingCompleted += new PingCompletedEventHandler(_myPing_PingCompleted);
                myPing.SendAsync(strScanIPAdd, 1000, null);
            }
            MessageBox.Show(IPList);
        }
        private void _myPing_PingCompleted(object sender, PingCompletedEventArgs e)
        {
            if (e.Reply.Status == IPStatus.Success)
            {
                IPList += e.Reply.Address.ToString()+"\n";
            }
        }