C#判斷本地系統的網路連接狀態

函數InternetGetConnectedState返回本地系統的網路連接狀態。

文法：

BOOL InternetGetConnectedState(__out LPDWORD lpdwFlags,__in DWORD dwReserved); 參數： lpdwFlags[out]指向一個變數，該變數接收串連描述內容。該參數在函數返回FLASE時仍可以返回一個有效標記。該參數可以為下列值的一個或多個。

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。 傳回值：當存在一個modem或一個LAN串連時，返回TRUE，當不存在internet串連或所有的串連當前未被啟用時，返回false。當該函數返回false時，程式可以調用 GetLastError來接收錯誤碼。 樣本：

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：        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();        }    }}

 

：