C#实现简单的 Ping 的功能，用于测试网络是否已经联通

 /// <summary>
         /// 是否能 Ping 通指定的主机
         /// </summary>
         /// <param name="ip">ip 地址或主机名或域名</param>
         /// <returns>true 通，false 不通</returns>
         public bool Ping(string ip)
         {
             System.Net.NetworkInformation.Ping p = new System.Net.NetworkInformation.Ping();
             System.Net.NetworkInformation.PingOptions options = new System.Net.NetworkInformation.PingOptions();
             options.DontFragment = true;
             string data = "Test Data!";
             byte[] buffer = Encoding.ASCII.GetBytes(data);
             int timeout = 1000; // Timeout 时间，单位：毫秒
             System.Net.NetworkInformation.PingReply reply = p.Send(ip, timeout, buffer, options);
             if (reply.Status == System.Net.NetworkInformation.IPStatus.Success)
                 return true;
             else
                 return false;
         }

http://www.cnblogs.com/anjou/archive/2007/10/11/920214.html