WinSCP uses SSH implementation from PuTTY project.
Smartcard authentication is on their wish list (though with a low priority):
https://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/smartcard-auth.html

Is there, or will there be support for CAC Authentication in WinSCP.Net?
If there is, can you post c# example code?

Thanks much,
Brian