函数原型：函数InternetGetConnectedState返回本地系统的网络连接状态。

语法：

BOOL InternetGetConnectedState(

__out LPDWORD lpdwFlags,

__in DWORD dwReserved

);

参数：

lpdwFlags[out]

指向一个变量，该变量接收连接描述内容。该参数在函数返回FLASE时仍可以返回一个有效的标记。该参数可以为下列值的一个或多个

值	含义
INTERNET_CONNECTION_CONFIGURED   0x40(64)	Local system has a valid connection to the Internet, but it might or might not be currently connected.
INTERNET_CONNECTION_LAN                   0x02(2)	Local system uses a local area network to connect to the Internet.
INTERNET_CONNECTION_MODEM0             x01(1)	Local system uses a modem to connect to the Internet.
INTERNET_CONNECTION_MODEM_BUSY0   x08(8)	No longer used.
INTERNET_CONNECTION_OFFLINE             0x20(16)	Local system is in offline mode.
INTERNET_CONNECTION_PROXY                0x04(4)	Local system uses a proxy server to connect to the Internet.
INTERNET_RAS_INSTALLED                        0x10(8)	Local system has RAS installed.

dwReserved[in]

保留值。必须为0。

当存在一个modem或一个LAN连接时，返回TRUE，当不存在internet连接或所有的连接当前未被激活时，返回false。

当该函数返回false时，程序可以调用

GetLastError来接收错误代码。

运行效果：

代码：

using System;using System.Collections.Generic;using System.Text;using System.Net.NetworkInformation;namespace ConsoleApplication1{    class Program    {        public static void Main(string[] args)        {            string url = "www.baidu.com;www.sina.com;www.cnblogs.com;www.google.com;www.163.com;www.csdn.com";            string[] urls = url.Split(new char[] { ';' });            CheckServeStatus(urls);            Console.ReadKey();        }                /// 
        /// 检测网络连接状态        /// 
        ///         public static void CheckServeStatus(string[] urls)        {            int errCount = 0;//ping时连接失败个数            if (!LocalConnectionStatus())            {                Console.WriteLine("网络异常~无连接");            }            else if (!MyPing(urls, out errCount))            {                if ((double)errCount / urls.Length >= 0.3)                {                    Console.WriteLine("网络异常~连接多次无响应");                }                else                {                    Console.WriteLine("网络不稳定");                }            }            else            {                Console.WriteLine("网络正常");            }        }        #region 网络检测         private const int INTERNET_CONNECTION_MODEM = 1;        private const int INTERNET_CONNECTION_LAN = 2;        [System.Runtime.InteropServices.DllImport("winInet.dll")]        private static extern bool InternetGetConnectedState(ref int dwFlag, int dwReserved);        /// 
        /// 判断本地的连接状态         /// 
        /// 
                 private static bool LocalConnectionStatus()        {            System.Int32 dwFlag = new Int32();            if (!InternetGetConnectedState(ref dwFlag, 0))            {                Console.WriteLine("LocalConnectionStatus--未连网!");                return false;            }            else            {                if ((dwFlag & INTERNET_CONNECTION_MODEM) != 0)                {                    Console.WriteLine("LocalConnectionStatus--采用调制解调器上网。");                    return true;                }                else if ((dwFlag & INTERNET_CONNECTION_LAN) != 0)                {                    Console.WriteLine("LocalConnectionStatus--采用网卡上网。");                    return true;                }            }            return false;        }        /// 
        /// Ping命令检测网络是否畅通        /// 
        /// URL数据        /// ping时连接失败个数        /// 
                 public static bool MyPing(string[] urls, out int errorCount)        {            bool isconn = true;            Ping ping = new Ping();            errorCount = 0;            try            {                PingReply pr;                for (int i = 0; i < urls.Length; i++)                {                    pr = ping.Send(urls[i]);                    if (pr.Status != IPStatus.Success)                    {                        isconn = false;                        errorCount++;                    }                    Console.WriteLine("Ping " + urls[i] + "    " + pr.Status.ToString());                }            }            catch            {                isconn = false;                errorCount = urls.Length;            }            //if (errorCount > 0 && errorCount < 3)            //  isconn = true;            return isconn;        }        #endregion    }}