Yeah, I may just answer

Gene,

The InterfaceManager.LastInterface is saved in the ScanController.Interface property setter. The LastInterface property takes the last saved interface ID and tries to find the matching NetworkInterface object.
As for setting one yourself, well, are you trying to hard-code in an interface to scan with? If so, you could set netInterface to the network interface you want to use (you can get a list of interfaces from NetworkInterface.GetAllNetworkInterfaces())