This code snippit will show you how to detect if there is a network link on one of the network adaptors on your system. The function is written in C# and uses the Windows Management Instrumentation to get the link status.

It is ready to use, as is. It has been used on many projects, personal and professional.

/// <summary>
/// Checks if a network is connected to the local machine.
/// </summary>
/// <returns>true if network connected, false if not</returns>   

static public bool IsNetworkConnected()
{
    bool connected=false;     if(SystemInformation.Network)   

    {
        System.Management.ManagementObjectSearcher searcher=new System.Management.ManagementObjectSearcher
                            ("SELECT NetConnectionStatus FROM Win32_NetworkAdapter");
        foreach(System.Management.ManagementObject networkAdapter in searcher.Get())
        {
            if(networkAdapter["NetConnectionStatus"]!=null)
            {
                if((int)networkAdapter["NetConnectionStatus"]==2)
                {
                    connected = true;
                    break;
                }
            }
        }
        searcher.Dispose();
    }
    return connected; }