CustomControllerdeviceInstanceGuid Property

The unique persistent instance GUID of this device. This is an id generated for the device that may stay constant between application sessions and system restarts. This can be used for device assignment persistence between runs. The specific platform and input sources in use affects the reliability of this value for device assignment persistence. A value of Guid.Empty means the device or input source has no reliable unique identifier so persistant assignment isn't possible using this value. Even if a Guid is provided, reliability when multiple identical controllers are attached depends greatly on the platform and input source(s) currently in use.

public override Guid deviceInstanceGuid { get; }