I am in need of a piece of code that can detect if a network connection is connected or disconnected. The connected state would mean a cable was plugged into the Ethernet connection. A disconnected state would mean there is not cable connected.
I can't use the WMI interface due to the fact that I'm running on Windows CE. I don't mind invoking the Win32 API but remember that I'm using Windows CE and running on the Compact Framework.
Check out this MSDN article:
Testing for and Responding to Network Connections in the .NET Compact Framework
One thing to remember is that a network connection is not equal to an internet connection.
It sounds like you already get that because you define connected as meaning "a cable is plugged into the Ethernet connection", but it bears repeating.
Call GetAdaptersInfo and loop through the list of available network adapters until you find the one you're looking for?
The easiest way is to use OpenNETCF's SDF and look at the OpenNETCF.Net.AdapterStatusMonitor class, which will raise events when NDIS sends out notifications (like MEDIA_CONNECT and MEDIA_DISCONNECT).
You can do the same work without the SDF, of course. It involves onening the NDIS driver directly and calling IOCTL_NDISUIO_REQUEST_NOTIFICATION with a P2P message queue handle. It's not overly difficult, but there's a lot you have to get right for it to work and not leak.