c#使用winnet检测网络连接状况

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

using System.Runtime.InteropServices;

namespace Pinyin

{

public partial class Form4 : Form

{

// 定义常量

private const long INTERNET_CONNECTION_MODEM = 1;//Local system uses a modem to connect to the Internet.

private const long INTERNET_CONNECTION_LAN = 2; //Local system uses a local area network to connect to the Internet.

private const long INTERNET_CONNECTION_PROXY = 4;//Local system uses a proxy server to connect to the Internet.

private const long INTERNET_CONNECTION_MODEM_BUSY = 8; //No longer used.

private const long INTERNET_CONNECTION_CONFIGURED = 64; //Local system has a valid connection to the Internet, but it might or might not be currently connected.

private const long INTERNET_CONNECTION_OFFLINE = 32; // Local system is in offline mode.

private const long INTERNET_RAS_INSTALLED = 16; //Local system has RAS installed.

public Form4()

{

InitializeComponent();

}

//定义（引用）API函数

[DllImport("wininet.dll")]

public static extern bool InternetGetConnectedState(out long lpdwFlags, long dwReserved);

private void button1_Click(object sender, EventArgs e)

{

long lfag;

string strConnectionDev = "";

if (InternetGetConnectedState(out lfag, 0))

strConnectionDev = "网络连接正常!";

else

strConnectionDev = "网络连接不可用!";

if ((lfag & INTERNET_CONNECTION_OFFLINE) > 0)

strConnectionDev += "OFFLINE 本地系统处于离线模式。";

if ((lfag & INTERNET_CONNECTION_MODEM) > 0)

strConnectionDev += "Modem 本地系统使用调制解调器连接到互联网。";

if ((lfag & INTERNET_CONNECTION_LAN) > 0)

strConnectionDev += "LAN 本地系统使用的局域网连接到互联网。";

if ((lfag & INTERNET_CONNECTION_PROXY) > 0)

strConnectionDev += "a Proxy";

if ((lfag & INTERNET_CONNECTION_MODEM_BUSY) > 0)

strConnectionDev += "Modem but modem is busy";

MessageBox.Show(strConnectionDev);

}

}

}