How to identify if a PV1 segment exists or not in an ORU_R01 message?

[sse-jtc]

I am using v251.

I would like to know if an IMessage contains an optional segment or not. In my case I have en ORU_R01 type that may or may not include a PV1 segment, but I cannot find a "proper" way to determine that.

I have tried using an ADT_A01 message. In this case I can use the IGroup.GetAll() method which seems to do the trick, but I fail to see that work for the ORU_R01 message. Maybe it has to do with me not knowing the right HL7 path expressions.

As a workaround I have tried using Terser.Finder.FindSegment("PV1",0) and then checking some of the properties of the segment. It can work, but I consider it to be a poor option as it could lead to other issues.

The below code shows an ORU_R01 message without a PV1 segment. In the bottom of the snippet I have added my attempts to identify the PV1 segment using various methods and HL7 path expressions.

ORU_R01 oruMessage = new ORU_R01();

// Populate the MSH segment
MSH mshSegment = oruMessage.MSH;
mshSegment.FieldSeparator.Value = "|";
mshSegment.EncodingCharacters.Value = "^~\\&";
mshSegment.SendingApplication.NamespaceID.Value = "SendingApp";
mshSegment.SendingFacility.NamespaceID.Value = "SendingFacility";
mshSegment.ReceivingApplication.NamespaceID.Value = "ReceivingApp";
mshSegment.ReceivingFacility.NamespaceID.Value = "ReceivingFacility";
mshSegment.DateTimeOfMessage.Time.Value  = DateTime.Now.ToString("yyyyMMddHHmmss");
mshSegment.MessageType.MessageCode.Value = "ORU";
mshSegment.MessageType.TriggerEvent.Value = "R01";
mshSegment.MessageControlID.Value = "12345";
mshSegment.ProcessingID.ProcessingID.Value = "P";
mshSegment.VersionID.VersionID.Value = "2.5.1";

// Populate the PID segment
PID pidSegment = oruMessage.GetPATIENT_RESULT().PATIENT.PID;
pidSegment.SetIDPID.Value = "1";
pidSegment.PatientID.IDNumber.Value = "123456";
pidSegment.GetPatientName(0).FamilyName.Surname.Value = "Doe";
pidSegment.GetPatientName(0).GivenName.Value = "John";
pidSegment.DateTimeOfBirth.Time.Value = "19800101";
pidSegment.AdministrativeSex.Value = "M";

// Populate the OBR segment
ORU_R01_ORDER_OBSERVATION orderObservation = oruMessage.GetPATIENT_RESULT().GetORDER_OBSERVATION();
OBR obrSegment = orderObservation.OBR;
obrSegment.SetIDOBR.Value = "1";
obrSegment.PlacerOrderNumber.EntityIdentifier.Value = "123456";
obrSegment.FillerOrderNumber.EntityIdentifier.Value = "654321";
obrSegment.UniversalServiceIdentifier.Identifier.Value = "TestCode";
obrSegment.ObservationDateTime.Time.Value = DateTime.Now.ToString("yyyyMMddHHmmss");

// Populate the OBX segment
OBX obxSegment = orderObservation.GetOBSERVATION().OBX;
obxSegment.SetIDOBX.Value = "1";
obxSegment.ValueType.Value = "TX";
obxSegment.ObservationIdentifier.Identifier.Value = "TestObservation";
obxSegment.Units.Identifier.Value = "mg/dL";
obxSegment.ReferencesRange.Value = "70-100";
obxSegment.ObservationResultStatus.Value = "F";

// Populate the PV1 segment
//PV1 pv1Segment = oruMessage.GetPATIENT_RESULT().PATIENT.VISIT.PV1;

var pv1 = oruMessage.GetPATIENT_RESULT().PATIENT.VISIT.PV1; //returns a PV1 object - I hoped for null
var pv1UsingGetAll1 = oruMessage.GetAll("PV1"); //throws exception no matter if I added the PV1 segment or not - I hoped for null if it does not exists
var pv1UsingGetAll2 = oruMessage.GetAll("PATIENT_RESULT/PATIENT/VISIT/PV1"); //throws exception no matter if I added the PV1 segment or not - I hoped for null if it does not exists