C#判斷本地系統的網絡連接狀態

函數InternetGetConnectedState返回本地系統的網絡連接狀態。

語法：

BOOL InternetGetConnectedState(

__out LPDWORD lpdwFlags,

__in DWORD dwReserved

);

 

參數：

lpdwFlags[out]

指向一個變量，該變量接收連接描述內容。該參數在函數返回FLASE時仍可以返回一個有效的標記。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。

 

返回值：

當存在一個modem或一個LAN連接時，返回TRUE，當不存在internet連接或所有的連接當前未被激活時，返回false。

當該函數返回false時，程序可以調用 GetLastError來接收錯誤代碼。

 

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 ")]

        //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();
        }
    }
}

 

截圖：