Question

在C#中有哪个函数是判断网络是否有链接?

Answer 1

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);
}
}
}