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_CONFIGURED0x40	Local system has a valid connection to the Internet, but it might or might not be currently connected.
INTERNET_CONNECTION_LAN 0x02	Local system uses a local area network to connect to the Internet.
INTERNET_CONNECTION_MODEM0x01	Local system uses a modem to connect to the Internet.
INTERNET_CONNECTION_MODEM_BUSY0x08	No longer used.
INTERNET_CONNECTION_OFFLINE 0x20	Local system is in offline mode.
INTERNET_CONNECTION_PROXY0x04	Local system uses a proxy server to connect to the Internet.
INTERNET_RAS_INSTALLED0x10	Local system has RAS installed.

dwReserved[in] 保留值。必须为0。 返回值： 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。 示例：

复制代码 代码如下:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Runtime.InteropServices;

namespace ConsoleApplication1

{

class Program

{

private const int INTERNET_CONNECTION_MODEM = 1;

private const int INTERNET_CONNECTION_LAN = 2;

private const int INTERNET_CONNECTION_PROXY = 4;

private const int INTERNET_CONNECTION_MODEM_BUSY = 8;

[DllImport("winInet.dll ")]

//声明外部的函数：

private static extern bool InternetGetConnectedState(

ref int Flag,

int dwReserved

);

static void Main(string[] args)

{

int Flag = 0;

string netStates = "";

if (!InternetGetConnectedState(ref Flag, 0))

{

Console.WriteLine("no！");

}

else

{

if ((Flag & INTERNET_CONNECTION_MODEM) != 0)

netStates += " Connect by MODEM /n";

if ((Flag & INTERNET_CONNECTION_LAN) != 0)

netStates += "Connect by LAN /n";

if ((Flag & INTERNET_CONNECTION_PROXY) != 0)

netStates += "Connect by PROXY /n";

if ((Flag & INTERNET_CONNECTION_MODEM_BUSY) != 0)

netStates += " MODEM is busy /n";

}

Console.WriteLine(netStates);

Console.ReadLine();

}

}

}

截图：