I wrote an application for the Windows Phone Marketplace, and it was rejected. I use the internal WebBrowser control, and I never tested it without the internet connection. Here is the hard part – the Emulator is always connected, there isn’t a way to turn it’s internet connection off (that I know of).
So I tested it on my phone, in airplane mode, and sure enough, it crashes.
Here is some code from MSDN that I was able to use to do some checking if there was internet access.
