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

class NetStatus
{
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.

[DllImport("wininet.dll")]

public static extern bool InternetGetConnectedState(out long lpdwFlags, long dwReserved);
public static string NetCheck()
{
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";

return strConnectionDev;
}
}

本文转自94cool博客园博客，原文链接：http://www.cnblogs.com/94cool/archive/2009/08/13/1545368.html，如需转载请自行联系原作者