值	含義
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。必須為0。

返回值：

當(dāng)存在一個(gè)modem或一個(gè)LAN連接時(shí)，返回TRUE，當(dāng)不存在internet連接或所有的連接當(dāng)前未被激活時(shí)，返回false。

當(dāng)該函數(shù)返回false時(shí)，程序可以調(diào)用GetLastError來接收錯(cuò)誤代碼。

示例：

復(fù)制代碼代碼如下:

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 ")] 

        //聲明外部的函數(shù)： 

        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(); 
        } 
    } 
}