用C#使用API即時判斷當前的網絡的連接方式

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace MeshworkLinkMode
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("使用InternetGetConnectedState對網絡連接方式進行判斷");
            Console.WriteLine(Fun_InternetGetConnectedState());
            Console.WriteLine("使用IsNetworkAlive對網絡連接方式進行判斷");
            Console.WriteLine(Fun_IsNetworkAlive());
            Console.ReadLine();
        }

        [DllImport("wininet.dll")]
        private extern static bool InternetGetConnectedState(out int connectionDescription, int reservedValue);

        [DllImport("sensapi.dll")]
        private extern static bool IsNetworkAlive(out int connectionDescription);

        static string Fun_InternetGetConnectedState()
        {
            int INTERNET_CONNECTION_MODEM = 1;
            int INTERNET_CONNECTION_LAN = 2;
            int INTERNET_CONNECTION_PROXY = 4;
            int INTERNET_CONNECTION_MODEM_BUSY = 8;

            string outPut = null;
            int flags;//上網方式
            bool m_bOnline = true;//是否在線

            m_bOnline = InternetGetConnectedState(out flags, 0);
            if (m_bOnline)//在線  
            {
                if ((flags & INTERNET_CONNECTION_MODEM) == INTERNET_CONNECTION_MODEM)
                {
                    outPut = "在線：撥號上網\n";
                }
                if ((flags & INTERNET_CONNECTION_LAN) == INTERNET_CONNECTION_LAN)
                {
                    outPut = "在線：通過局域網\n";
                }
                if ((flags & INTERNET_CONNECTION_PROXY) == INTERNET_CONNECTION_PROXY)
                {
                    outPut = "在線：代理\n";
                }
                if ((flags & INTERNET_CONNECTION_MODEM_BUSY) == INTERNET_CONNECTION_MODEM_BUSY)
                {
                    outPut = "MODEM被其他非INTERNET連接佔用\n";
                }
            }
            else
            {
                outPut = "不在線\n";
            }

            return outPut;
        }

        static string Fun_IsNetworkAlive()
        {
            int NETWORK_ALIVE_LAN = 0;
            int NETWORK_ALIVE_WAN = 2;
            int NETWORK_ALIVE_AOL = 4;

            string outPut = null;
            int flags;//上網方式
            bool m_bOnline = true;//是否在線

            m_bOnline = IsNetworkAlive(out flags);
            if (m_bOnline)//在線  
            {
                if ((flags & NETWORK_ALIVE_LAN) == NETWORK_ALIVE_LAN)
                {
                    outPut = "在線：NETWORK_ALIVE_LAN\n";
                }
                if ((flags & NETWORK_ALIVE_WAN) == NETWORK_ALIVE_WAN)
                {
                    outPut = "在線：NETWORK_ALIVE_WAN\n";
                }
                if ((flags & NETWORK_ALIVE_AOL) == NETWORK_ALIVE_AOL)
                {
                    outPut = "在線：NETWORK_ALIVE_AOL\n";
                }
            }
            else
            {
                outPut = "不在線\n";
            }

            return outPut;
        }
    }
}

說明：
InternetGetConnectedState()：對網絡狀況不能及時反應
IsNetworkAlive()：可以及時反應網絡連通情況，但是需要服務System Event Notification支持（系統默認自動啓動該服務）。使用該函數，需要安裝最新的SDK（如.net的）