How can I write a program in c# on Windows that can read and write to NFC cards?. Open source / commercial are both fine. Thanks
Contact Stollmann: http://www.stollmann.de/en/home and ask for the Windows NFC stack or the windows NFC Dev-Kit.
Disclaimer: I work for stollmann, and I'm one of the engineers who did the NFC on Android, Windows and Linux (and more) platform solution. Yes, I promote my own product here.. Otoh as far as I know it's the only product out there that offers modern NFC-functionality on the Windows platform.