public OperationOutcome ValidatePatientReference(ResourceReference reference) { if (!_validationHelper.ValidReference(reference, FhirConstants.SystemPDS)) { return(OperationOutcomeFactory.CreateInvalidResource("subject")); } var nhsNumber = reference.Reference.Replace(FhirConstants.SystemPDS, ""); if (!_validationHelper.ValidNhsNumber(nhsNumber)) { return(OperationOutcomeFactory.CreateInvalidNhsNumberRes(nhsNumber)); } return(null); }