Creating Entity in People do not update EntitySet

[quanterion]

TripPin RW test service for OData doesn't show added entities.
When I add entity (Person) via POST https://services.odata.org/V4/(S(xxx))/TripPinServiceRW  service responses with 204 Created. But listing of persons via GET https://services.odata.org/V4/(S(xxx))/TripPinServiceRW remains the same and I can't see added person.

[mikepizzo]

Code appears to attempt to add the person to the datasource instance. Perhaps the instance isn't being maintained, so it is adding to a different instance than it is retrieving from?

I also tried against https://services.odata.org/TripPinRESTierService, but got a server error (Value cannot be null. Parameter name: edmEntityObject) when posting the person (which we should create a separate issue to investigate).