微软提供的函数不能再多网卡的情况下，判断指定网卡的网线连接状态。以下代码刚好能够解决这个问题。

   using System;  using System.Collections.Generic;  using System.Linq;  using System.Text;  using System.Net.NetworkInformation;  using System.Threading;      namespace NetworkAdapterTestEvent  {      class Program      {          static void Main(string[] args)          {              NetworkAdapterAvailable newtest = new NetworkAdapterAvailable();                  newtest.Subscribe("本地连接",new NetworkAdapterAvailable.NetworkAdapterChangedEventHandler(NetowrkAdapter_changed));              newtest.StartMonitor();                  Console.ReadLine();              newtest.StopMonitor();              newtest.Unsubscribe("本地连接", new NetworkAdapterAvailable.NetworkAdapterChangedEventHandler(NetowrkAdapter_changed));          }              static void NetowrkAdapter_changed(object sender, NetworkAdapterChangedArgument e)          {              Console.WriteLine("Name:{0}\\tStatus:{1}", e.AdapterName, e.AdapterStatus.ToString());          }      }          public class NetworkAdapterAvailable      {          public delegate void NetworkAdapterChangedEventHandler(object send , NetworkAdapterChangedArgument e);                      public event NetworkAdapterChangedEventHandler NetworkAdapterChanged;              private Thread _AdapterCheckThread;          private string _AdapterName;          private bool _Stop = false;          private NetworkInterface[] _adapters;              public NetworkAdapterAvailable()          {              _adapters = NetworkInterface.GetAllNetworkInterfaces();          }              /// <summary>          /// 订阅          /// </summary>          /// <param name="_adaptername_"></param>          /// <param name="_EventHandler_"></param>          public void Subscribe(string _adaptername_ , NetworkAdapterChangedEventHandler _EventHandler_)          {              _AdapterName = _adaptername_;                  if (_EventHandler_ != null)              {                  NetworkAdapterChanged += _EventHandler_;              }          }              /// <summary>          /// 取消订阅          /// </summary>          /// <param name="_adaptername_"></param>          /// <param name="_EventHandler_"></param>          public void Unsubscribe(string _adaptername_, NetworkAdapterChangedEventHandler _EventHandler_)          {              if (_EventHandler_ != null)              {                  NetworkAdapterChanged -= _EventHandler_;              }          }              /// <summary>          /// 开始监控          /// </summary>          public void StartMonitor()          {              _AdapterCheckThread = new Thread(new ThreadStart(AdapterCheckHandler));              _AdapterCheckThread.IsBackground = true;              _AdapterCheckThread.Start();          }              public void StopMonitor()          {              _Stop = true;                  if (_AdapterCheckThread != null)              {                  _AdapterCheckThread.Join();              }              }              private void AdapterCheckHandler()          {              while (!_Stop)              {                  NetworkInterface[] __adapters = NetworkInterface.GetAllNetworkInterfaces();                      for (int i = 0; i < __adapters.Length; i++)                  {                      if (_adapters[i].Name == _AdapterName)                      {                          if (_adapters[i].OperationalStatus != __adapters[i].OperationalStatus)                          {                              NetworkAdapterChanged(this, new NetworkAdapterChangedArgument(_AdapterName, __adapters[i].OperationalStatus));                              _adapters[i] = __adapters[i];                          }                      }                  }                      Thread.Sleep(100);              }          }      }          public class NetworkAdapterChangedArgument : EventArgs      {          private string _AdapterName;          private OperationalStatus _AdapterStatus;              public NetworkAdapterChangedArgument(string _adaptername_, OperationalStatus _adapterstatus_)          {              _AdapterName = _adaptername_;              _AdapterStatus = _adapterstatus_;          }              public string AdapterName          {              get { return _AdapterName; }          }              public OperationalStatus AdapterStatus          {              get { return _AdapterStatus; }          }      }  }