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C#中判断本地系统的网络连接状态的方法

2018-10-12 14:08 441 查看

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：

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