JoysticksystemId Property

The id of the device in the underlying input source. The meaning of this value is determined by the current input source. This may include Unity input, Raw Input, Direct Input, OSX I/O Kit, XBoxOneInput, Ouya input, and others. Generally, you should never need to use this, but it is exposed for advanced uses. Returns null if there is no system id associated with this joystick.

public Nullable<long> systemId { get; }