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：
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：
