c#获取外网IP地址的方法

//获取宽带连接(PPPOE拨号)的IP地址，timeout超时(秒)，当宽带未连接或者连接中的时候获取不到IP
        public static string GetIP_PPPOE(int timeout)
        {
            int i = timeout * 2;
            while (i > 0)
            {
                try
                {
                    NetworkInterface[] nics = NetworkInterface.GetAllNetworkInterfaces();
                    bool havePPPOE = false;
                    foreach (NetworkInterface adapter in nics)
                    {
                        if (adapter.NetworkInterfaceType == NetworkInterfaceType.Ppp)
                        {
                            havePPPOE = true;
                            IPInterfaceProperties ip = adapter.GetIPProperties();     //IP配置信息
                            if (ip.UnicastAddresses.Count > 0)
                            {
                                return ip.UnicastAddresses[0].Address.ToString();
                            }
                        }
                    }
                    //当没有宽带连接的时候直接返回空
                    if (!havePPPOE) return "";
                }
                catch (Exception ex)
                {
                    Console.WriteLine("获取宽带拨号IP出错:" + ex.Message);
                }
                i--;
                Thread.Sleep(500);
            }
            return "";
        }