How do you determine if an Internet connection is available for your WinForms App?

Question

What is the best way to determine whether there is an available Internet connection for a WinForms app. (Programatically of course) I want to disable/hide certain functions

Answer 1

sbeskur's response has a bug in the translation of InternetGetConnectedState. The parameters are both DWORD's (first one is an LPDWORD). Both of these translate to int's in C# (technically, uint but int will work for most scenarios).

Correct translation below.

[DllImport("wininet.dll", SetLastError=true)] 
public static extern bool InternetGetConnectedState(out int flags,int reserved);