Encountered unknown element 'subject' Error

Using C#.Net HL 7 library, created a Condition FHIR Resource and trying to link to its Patient Resource using condition.subject property. But keep getting below error:
Operation was unsuccessful because of a client error (BadRequest). OperationOutcome: Overall result: FAILURE (1 errors and 0 warnings)

[ERROR] (no details)(further diagnostics: Body parsing failed: Type checking the data: Encountered unknown element ‘subject’ at location ‘Resource.subject[0]’ while parsing).
Any idea?


Already raised here: https://chat.fhir.org/#narrow/stream/179166-implementers/topic/Encountered.20unknown.20element.20’subject’.20Error