如何确定网络接口是否连接到Internet（即计算机是否在线）

Question

I need a way to determine internet availability programmatically. At now i use Ping to constantly ping some internet site.

But it seems Windows 7 though determines internet availability in some other way. If computer is online there is earth icon on the network interface icon in the System Tray.

The question is: is there any standard Win32 way to check online status, win event or something, and if so, how to use it from C#?

Answer 1

I believe something like this would work although your question appears to be a duplicate:

using System;
using System.Runtime;
using System.Runtime.InteropServices;

public class InternetCS
{
    //Creating the extern function...
    [DllImport("wininet.dll")]
    private extern static bool InternetGetConnectedState( out int Description, int ReservedValue );

    //Creating a function that uses the API function...
    public static bool IsConnectedToInternet( )
    {
        int Desc ;
        return InternetGetConnectedState( out Desc, 0 ) ;
    }
}

forund here:

check whether Internet connection is available with C#

Answer 2

'Connected to the Internet' doesn't have any actual meaning except in the case of a modem. The beat way to test whether any resource is available is to use it. You have to cope with failures at that point anyway, no need to code everything twice.