I need a event to detect Internet connect/disconnect

We are developing a .NET application where one of the requirements is to monitor whether the system is connected to the internet or not.

We were able to get a .NET event for "ethernet cable disconnect", but if the modem is reset then this event does not get triggered. I don't want to keep pinging some URL to get this done since it will add considerable performance overhead. Is there any .NET event which can check whether the system is connected to the internet or not?

There is an icon in system tray which shows a cross sign or limited connectivity sign when the system is not conncected to the internet. That suggests Windows knows, and I want to trap that event.

Solution 1:

You can use the NetworkChange class, with the NetworkAvailabilityChanged event:

NetworkChange.NetworkAvailabilityChanged += myNetworkAvailabilityChangeHandler;

Since it's a system event, make sure you delete the event when you're finished, see this post here: You need to be careful about using event handler for NetworkChange

Solution 2:

This is all covered (including the difference between being on the network and having the network connect you to the Internet) at http://msdn.microsoft.com/en-us/library/ee264321(VS.85).aspx. I hope you meant to put that Windows 7 tag on your post, because all this is pretty new.

The key is INetworkListManager.get_IsConnectedToInternet() which pretty much does what it says on the tin. You have to jump around a bit to register for the events etc. The Code Pack wraps some of that up for you and has a network sample you can adapt.

Solution 3:

I was able to solve this problem to some extent. I was able to find some sample code in Code project http://www.codeproject.com/script/Articles/ListVersions.aspx?aid=34650. Thanks all for the replies.

especially the article link which was posted by Ms Gregory helped me a lot.

Solution 4:

This worked for me!

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.NetworkInformation;
namespace ConsoleApplication6
{


    class Program
    {
        private void AvailabilityChanged(object sender, NetworkAvailabilityEventArgs e)
        {

            if (e.IsAvailable)
                Console.WriteLine("Network connected!");
            else
                Console.WriteLine("Network dis connected!");
        }
        public void Form1()
        {

            NetworkChange.NetworkAvailabilityChanged += AvailabilityChanged;
        }

        static void Main(string[] args)
        {
            Program p = new Program();

            p.Form1();

            Console.ReadLine();

        }
    }
}