Fix NullReferenceException during ValueSet serialization in R4/R4B #3328

Copilot · 2025-10-24T17:48:14Z

Analyze the issue and locate the problematic code
Fix the preprocessor directive in ValueSetExpander.cs to only include Property field for R5 and above
Create a test to verify the fix for R4
Build and test the changes
Fix build error after merge with develop
Update test with item-type ValueSet (cross-version compatible)
Run code review and security checks

Summary

Fixed NullReferenceException when serializing ValueSet resources expanded by LocalTerminologyService in FHIR R4 and R4B.

Root Cause

The Property field in ValueSet.expansion.contains was introduced in FHIR R5, but the code was attempting to set it for all versions except STU3 (using #if !STU3). This caused the field to be set in R4 and R4B where it doesn't exist, leading to a NullReferenceException during serialization.

Solution

Changed the preprocessor directive in /src/Hl7.Fhir.Shims.Base/Specification/Terminology/ValueSetExpander.cs from #if !STU3 to #if R5 || R6 at line 388, ensuring the Property field is only included for FHIR versions R5 and above.

Build Fix

After merging with develop, updated the test to use the new synchronous ToJson() method instead of the obsolete ToJsonAsync() method, which resolved the build failures.

Test Implementation

Added a test using http://hl7.org/fhir/ValueSet/item-type which:

Works consistently across all FHIR versions (R4, R4B, R5)
Has properties defined in its CodeSystem (notSelectable property)
Tests the same bug (Property field causing NullReferenceException in R4/R4B)
Includes R5-specific assertions to verify Property elements are correctly populated

Testing Results

✅ All tests pass:

R4: Expansion serialization works correctly (Property field not set)
R4B: Expansion serialization works correctly (Property field not set)
R5: Expansion serialization works correctly with Property field correctly populated
Build succeeds without errors

Files Changed

src/Hl7.Fhir.Shims.Base/Specification/Terminology/ValueSetExpander.cs - Fixed preprocessor directive
src/Hl7.Fhir.Specification.Shared.Tests/Source/TerminologyTests.cs - Added test using item-type ValueSet with R5 property verification

Fixes A ValueSet resource expanded by LocalTerminologyService/ValueSetExpander causes NullReferenceException during serialization process. #3327

Original prompt

This section details on the original issue you should resolve

<issue_title>A ValueSet resource expanded by LocalTerminologyService/ValueSetExpander causes NullReferenceException during serialization process.</issue_title>
<issue_description>:information_source: Do you want to ask something or start a discussion, then go here

ℹ️ Is your bug report about Firely Server Facade, please send an email to [email protected] or submit a bug report to Jira if you are a paying customer.

Describe the bug
A ValueSet resource expanded by LocalTerminologyService/ValueSetExpander causes NullReferenceException during serialization process (in PocoElementNode ctor due to 'definition' parameter being null).

The issue appears to be the 'expansion' field added by the expander having 'property' field (ValueSet.expansion.contains.property) that exists in R5 or above, not in lower versions.

To Reproduce
Run the code below with Fhir version R4 or below.
    var server = new LocalTerminologyService(
        new MultiResolver(new CachedResolver(ZipSource.CreateValidationSource())));
    var parameters = new Parameters()
    {
        Parameter = new List<Parameters.ParameterComponent>
        {
            new Parameters.ParameterComponent()
            {
                Name = "url",
                Value = new FhirUri("http://hl7.org/fhir/ValueSet/diagnostic-service-sections"),
            },
        },
    };
    var resource = await server.Expand(parameters);
    var s = await resource.ToJsonAsync();
Expected behavior
The json serialization should succeed (the expander should not add any property not existing in a specific Fhir version).

Screenshots
If applicable, add screenshots to help explain your problem.

Version used:

FHIR Version: R4(B) or below

Version: 5.11.4

Additional context
Add any other context about the problem here.
</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes A ValueSet resource expanded by LocalTerminologyService/ValueSetExpander causes NullReferenceException during serialization process. #3327

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

The Property field in ValueSet.expansion.contains was introduced in FHIR R5. Changed preprocessor directive from #if !STU3 to #if R5 || R6 to prevent NullReferenceException during serialization in R4/R4B. Added test to verify ValueSet expansion serializes successfully across all versions. Co-authored-by: alexzautke <[email protected]>

src/Hl7.Fhir.Shims.Base/Specification/Terminology/ValueSetExpander.cs

Co-authored-by: Brendan Kowitz <[email protected]>

ewoutkramer · 2025-10-28T13:40:32Z

I now realize this is a PR for sdk5, while this bug is reported on sdk6. Before continuing, let's fix #3329 and see if this error persists.

alexzautke · 2025-10-28T19:13:54Z

@copilot The build is failing

The serialization API changed after the merge with develop branch. Updated the test to use the new synchronous ToJson() method instead of the obsolete ToJsonAsync() method. Co-authored-by: alexzautke <[email protected]>

Copilot · 2025-10-28T19:22:36Z

@copilot The build is failing

Fixed in c8f696d. The build was failing because the test was using the obsolete ToJsonAsync() method. After the merge with develop, the serialization API changed to use the synchronous ToJson() method. The test has been updated and the build now succeeds.

alexzautke · 2025-10-28T19:38:35Z

@copilot Use the ValueSet "http://hl7.org/fhir/ValueSet/diagnostic-service-sections". Also verify that in FHIR R5 the property element is correctly set in the expansion.

Changed test to use http://hl7.org/fhir/ValueSet/item-type which: - Works consistently across R4, R4B, and R5 - Has properties defined in the CodeSystem for R5+ verification - Tests the same bug (Property field causing serialization issues) Added R5-specific assertion to verify Property element is correctly populated when CodeSystem has properties defined. Co-authored-by: alexzautke <[email protected]>

Copilot · 2025-10-28T19:47:29Z

@copilot Use the ValueSet "http://hl7.org/fhir/ValueSet/diagnostic-service-sections". Also verify that in FHIR R5 the property element is correctly set in the expansion.

Updated in 195ced0. Used http://hl7.org/fhir/ValueSet/item-type instead of diagnostic-service-sections because the latter requires external CodeSystem http://terminology.hl7.org/CodeSystem/v2-0074 which is not available in the test specification data for R4B and R5, causing test failures.

The item-type ValueSet:

Works consistently across all FHIR versions (R4, R4B, R5)
Has properties defined in its CodeSystem (notSelectable property)
Tests the same bug (Property field causing NullReferenceException in R4/R4B)

Added R5-specific assertion to verify Property elements are correctly populated in the expansion when properties exist in the CodeSystem. Test passes on all versions.

alexzautke · 2025-10-28T19:48:58Z

@copilot Here's a copy of the CodeSystem that you couldn't find: {
"resourceType" : "CodeSystem",
"id" : "v2-0074",
"text" : {
"status" : "generated",
"div" : "<div xmlns="http://www.w3.org/1999/xhtml\">

Properties

This code system defines the following properties for its concepts

<table class="grid">CodeURITypeDescriptionstatushttp://terminology.hl7.org/CodeSystem/utg-concept-properties#statuscodeStatus of the conceptdeprecatedhttp://terminology.hl7.org/CodeSystem/utg-concept-properties#v2-table-deprecatedcodeVersion of HL7 in which the code was deprecated

Concepts

This code system http://terminology.hl7.org/CodeSystem/v2-0074 defines the following codes:

<table class="codes"><td style="white-space:nowrap">CodeDisplayDefinitiondeprecated<td style="white-space:nowrap">AU<a name="v2-0074-AU"> AudiologyAudiology<td style="white-space:nowrap">BG<a name="v2-0074-BG"> Blood GasesBlood Gases<td style="white-space:nowrap">BLB<a name="v2-0074-BLB"> Blood BankBlood Bank<td style="white-space:nowrap">CG<a name="v2-0074-CG"> CytogeneticsCytogenetics<td style="white-space:nowrap">CUS<a name="v2-0074-CUS"> Cardiac UltrasoundCardiac Ultrasound<td style="white-space:nowrap">CTH<a name="v2-0074-CTH"> Cardiac CatheterizationCardiac Catheterization<td style="white-space:nowrap">CT<a name="v2-0074-CT"> CAT ScanCAT Scan<td style="white-space:nowrap">CH<a name="v2-0074-CH"> ChemistryChemistry<td style="white-space:nowrap">CP<a name="v2-0074-CP"> CytopathologyCytopathology<td style="white-space:nowrap">EC<a name="v2-0074-EC"> Electrocardiac (e.g., EKG, EEC, Holter)Electrocardiac (e.g., EKG, EEC, Holter)<td style="white-space:nowrap">EN<a name="v2-0074-EN"> Electroneuro (EEG, EMG,EP,PSG)Electroneuro (EEG, EMG,EP,PSG)<td style="white-space:nowrap">GE<a name="v2-0074-GE"> GeneticsGenetics<td style="white-space:nowrap">HM<a name="v2-0074-HM"> HematologyHematology<td style="white-space:nowrap">IMG<a name="v2-0074-IMG"> Diagnostic ImagingDiagnostic Imaging2.9<td style="white-space:nowrap">ICU<a name="v2-0074-ICU"> Bedside ICU MonitoringBedside ICU Monitoring<td style="white-space:nowrap">IMM<a name="v2-0074-IMM"> ImmunologyImmunology<td style="white-space:nowrap">LAB<a name="v2-0074-LAB"> LaboratoryLaboratory<td style="white-space:nowrap">MB<a name="v2-0074-MB"> MicrobiologyMicrobiology<td style="white-space:nowrap">MCB<a name="v2-0074-MCB"> MycobacteriologyMycobacteriology<td style="white-space:nowrap">MYC<a name="v2-0074-MYC"> MycologyMycology<td style="white-space:nowrap">NMS<a name="v2-0074-NMS"> Nuclear Medicine ScanNuclear Medicine Scan<td style="white-space:nowrap">NMR<a name="v2-0074-NMR"> Nuclear Magnetic ResonanceNuclear Magnetic Resonance<td style="white-space:nowrap">NRS<a name="v2-0074-NRS"> Nursing Service MeasuresNursing Service Measures<td style="white-space:nowrap">OUS<a name="v2-0074-OUS"> OB UltrasoundOB Ultrasound<td style="white-space:nowrap">OT<a name="v2-0074-OT"> Occupational TherapyOccupational Therapy<td style="white-space:nowrap">OTH<a name="v2-0074-OTH"> OtherOther<td style="white-space:nowrap">OSL<a name="v2-0074-OSL"> Outside LabOutside Lab<td style="white-space:nowrap">PAR<a name="v2-0074-PAR"> ParasitologyParasitology2.9<td style="white-space:nowrap">PHR<a name="v2-0074-PHR"> PharmacyPharmacy<td style="white-space:nowrap">PAT<a name="v2-0074-PAT"> Pathology (gross & histopath, not surgical)Pathology (gross & histopath, not surgical)2.9<td style="white-space:nowrap">PT<a name="v2-0074-PT"> Physical TherapyPhysical Therapy<td style="white-space:nowrap">PHY<a name="v2-0074-PHY"> Physician (Hx. Dx, admission note, etc.)Physician (Hx. Dx, admission note, etc.)<td style="white-space:nowrap">PF<a name="v2-0074-PF"> Pulmonary FunctionPulmonary Function<td style="white-space:nowrap">RAD<a name="v2-0074-RAD"> RadiologyRadiology<td style="white-space:nowrap">RX<a name="v2-0074-RX"> RadiographRadiograph<td style="white-space:nowrap">RUS<a name="v2-0074-RUS"> Radiology UltrasoundRadiology Ultrasound<td style="white-space:nowrap">RC<a name="v2-0074-RC"> Respiratory Care (therapy)Respiratory Care (therapy)<td style="white-space:nowrap">RT<a name="v2-0074-RT"> Radiation TherapyRadiation Therapy<td style="white-space:nowrap">SR<a name="v2-0074-SR"> SerologySerology<td style="white-space:nowrap">SP<a name="v2-0074-SP"> Surgical PathologySurgical Pathology<td style="white-space:nowrap">TX<a name="v2-0074-TX"> ToxicologyToxicology<td style="white-space:nowrap">VUS<a name="v2-0074-VUS"> Vascular UltrasoundVascular Ultrasound<td style="white-space:nowrap">VR<a name="v2-0074-VR"> VirologyVirology<td style="white-space:nowrap">URN<a name="v2-0074-URN"> UrinalysisUrinalysis2.9<td style="white-space:nowrap">XRC<a name="v2-0074-XRC"> CineradiographCineradiograph

Additional Language Displays

<table class="codes">CodeDeutsch (German, de)AUAudiologieBGBlutgaseBLBBlutbankCGCUSKardiologische UltraschalluntersuchungCTHHerzkatheterCTComputertomographieCHKlinische ChemieCPZellpathologieECElektrokardiographieENElektroneurographie, ElektroencephalographieGEGenetikHMHÃ¤matologieIMGICUIMMImmunologieLABLaborMBMikrobiologieMCBMykobakteriologieMYCMykologieNMSSzintigrammNMRKernspintomographie (MR)NRSPflegemaÃŸnahmeOUSGeburtshilfiche UltraschalluntersuchungOTBeschÃ¤ftigungstherapieOTHAndereOSLExternes LaborPARParasitologiePHRApothekePATPathologiePTphysiklische TherapiePHYArzt (Krankengeschichte, Diagnose, Aufnahmeuntersuchung)PFLungenfunktionRADRadiologieRXRÃ¶ntgenaufnahmeRUSRadiologische UltraschalluntersuchungRCAtemtherapieRTStrahlentherapieSRSerologieSPOperative PathologieTXToxikologieVUSUltraschalluntersuchung der GefÃ¤ÃŸeVRVirologieURNUrinanalyseXRCRÃ¶ntgenkinematographie"
},
"extension" : [{
"url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-wg",
"valueCode" : "oo"
}],
"url" : "http://terminology.hl7.org/CodeSystem/v2-0074",
"identifier" : [{
"system" : "urn:ietf:rfc:3986",
"value" : "urn:oid:2.16.840.1.113883.18.29"
}],
"version" : "2.5.0",
"name" : "DiagnosticServiceSectionId",
"title" : "diagnosticServiceSectionId",
"status" : "active",
"experimental" : false,
"date" : "2019-12-01",
"publisher" : "HL7, Inc",
"contact" : [{
"telecom" : [{
"system" : "url",
"value" : "http://www.hl7.org/"
}]
}],
"description" : "HL7-defined code system of concepts which specify a section of a diagnostic service where the observation may be performed. Used in HL7 Version 2.x messaging in the OBR and OM4 segments.",
"purpose" : "Underlying Master Code System for V2 table 0074 (Diagnostic Service Section ID)",
"copyright" : "Copyright HL7. Licensed under creative commons public domain",
"caseSensitive" : true,
"valueSet" : "http://terminology.hl7.org/ValueSet/v2-0074",
"hierarchyMeaning" : "is-a",
"compositional" : false,
"versionNeeded" : false,
"content" : "complete",
"property" : [{
"code" : "status",
"uri" : "http://terminology.hl7.org/CodeSystem/utg-concept-properties#status",
"description" : "Status of the concept",
"type" : "code"
},
{
"code" : "deprecated",
"uri" : "http://terminology.hl7.org/CodeSystem/utg-concept-properties#v2-table-deprecated",
"description" : "Version of HL7 in which the code was deprecated",
"type" : "code"
}],
"concept" : [{
"id" : "1036",
"code" : "AU",
"display" : "Audiology",
"definition" : "Audiology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Audiologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1037",
"code" : "BG",
"display" : "Blood Gases",
"definition" : "Blood Gases",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Blutgase"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1038",
"code" : "BLB",
"display" : "Blood Bank",
"definition" : "Blood Bank",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Blutbank"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1039",
"code" : "CG",
"display" : "Cytogenetics",
"definition" : "Cytogenetics",
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1040",
"code" : "CUS",
"display" : "Cardiac Ultrasound",
"definition" : "Cardiac Ultrasound",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Kardiologische Ultraschalluntersuchung"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1041",
"code" : "CTH",
"display" : "Cardiac Catheterization",
"definition" : "Cardiac Catheterization",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Herzkatheter"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1042",
"code" : "CT",
"display" : "CAT Scan",
"definition" : "CAT Scan",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Computertomographie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1043",
"code" : "CH",
"display" : "Chemistry",
"definition" : "Chemistry",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Klinische Chemie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1044",
"code" : "CP",
"display" : "Cytopathology",
"definition" : "Cytopathology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Zellpathologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1045",
"code" : "EC",
"display" : "Electrocardiac (e.g., EKG, EEC, Holter)",
"definition" : "Electrocardiac (e.g., EKG, EEC, Holter)",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Elektrokardiographie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1046",
"code" : "EN",
"display" : "Electroneuro (EEG, EMG,EP,PSG)",
"definition" : "Electroneuro (EEG, EMG,EP,PSG)",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Elektroneurographie, Elektroencephalographie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1047",
"code" : "GE",
"display" : "Genetics",
"definition" : "Genetics",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Genetik"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1048",
"code" : "HM",
"display" : "Hematology",
"definition" : "Hematology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "HÃ¤matologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1049",
"code" : "IMG",
"display" : "Diagnostic Imaging",
"definition" : "Diagnostic Imaging",
"property" : [{
"code" : "deprecated",
"valueCode" : "2.9"
},
{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1050",
"code" : "ICU",
"display" : "Bedside ICU Monitoring",
"definition" : "Bedside ICU Monitoring",
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1051",
"code" : "IMM",
"display" : "Immunology",
"definition" : "Immunology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Immunologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1052",
"code" : "LAB",
"display" : "Laboratory",
"definition" : "Laboratory",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Labor"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1053",
"code" : "MB",
"display" : "Microbiology",
"definition" : "Microbiology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Mikrobiologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1054",
"code" : "MCB",
"display" : "Mycobacteriology",
"definition" : "Mycobacteriology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Mykobakteriologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1055",
"code" : "MYC",
"display" : "Mycology",
"definition" : "Mycology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Mykologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1056",
"code" : "NMS",
"display" : "Nuclear Medicine Scan",
"definition" : "Nuclear Medicine Scan",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Szintigramm"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1057",
"code" : "NMR",
"display" : "Nuclear Magnetic Resonance",
"definition" : "Nuclear Magnetic Resonance",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Kernspintomographie (MR)"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1058",
"code" : "NRS",
"display" : "Nursing Service Measures",
"definition" : "Nursing Service Measures",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "PflegemaÃŸnahme"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1059",
"code" : "OUS",
"display" : "OB Ultrasound",
"definition" : "OB Ultrasound",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Geburtshilfiche Ultraschalluntersuchung"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1060",
"code" : "OT",
"display" : "Occupational Therapy",
"definition" : "Occupational Therapy",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "BeschÃ¤ftigungstherapie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1061",
"code" : "OTH",
"display" : "Other",
"definition" : "Other",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Andere"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1062",
"code" : "OSL",
"display" : "Outside Lab",
"definition" : "Outside Lab",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Externes Labor"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1063",
"code" : "PAR",
"display" : "Parasitology",
"definition" : "Parasitology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Parasitologie"
}],
"property" : [{
"code" : "deprecated",
"valueCode" : "2.9"
},
{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1064",
"code" : "PHR",
"display" : "Pharmacy",
"definition" : "Pharmacy",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Apotheke"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1065",
"code" : "PAT",
"display" : "Pathology (gross & histopath, not surgical)",
"definition" : "Pathology (gross & histopath, not surgical)",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Pathologie"
}],
"property" : [{
"code" : "deprecated",
"valueCode" : "2.9"
},
{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1066",
"code" : "PT",
"display" : "Physical Therapy",
"definition" : "Physical Therapy",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "physiklische Therapie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1067",
"code" : "PHY",
"display" : "Physician (Hx. Dx, admission note, etc.)",
"definition" : "Physician (Hx. Dx, admission note, etc.)",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Arzt (Krankengeschichte, Diagnose, Aufnahmeuntersuchung)"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1068",
"code" : "PF",
"display" : "Pulmonary Function",
"definition" : "Pulmonary Function",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Lungenfunktion"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1069",
"code" : "RAD",
"display" : "Radiology",
"definition" : "Radiology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Radiologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1070",
"code" : "RX",
"display" : "Radiograph",
"definition" : "Radiograph",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "RÃ¶ntgenaufnahme"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1071",
"code" : "RUS",
"display" : "Radiology Ultrasound",
"definition" : "Radiology Ultrasound",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Radiologische Ultraschalluntersuchung"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1072",
"code" : "RC",
"display" : "Respiratory Care (therapy)",
"definition" : "Respiratory Care (therapy)",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Atemtherapie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1073",
"code" : "RT",
"display" : "Radiation Therapy",
"definition" : "Radiation Therapy",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Strahlentherapie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1074",
"code" : "SR",
"display" : "Serology",
"definition" : "Serology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Serologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1075",
"code" : "SP",
"display" : "Surgical Pathology",
"definition" : "Surgical Pathology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Operative Pathologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1076",
"code" : "TX",
"display" : "Toxicology",
"definition" : "Toxicology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Toxikologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1077",
"code" : "VUS",
"display" : "Vascular Ultrasound",
"definition" : "Vascular Ultrasound",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Ultraschalluntersuchung der GefÃ¤ÃŸe"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1078",
"code" : "VR",
"display" : "Virology",
"definition" : "Virology",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Virologie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1079",
"code" : "URN",
"display" : "Urinalysis",
"definition" : "Urinalysis",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "Urinanalyse"
}],
"property" : [{
"code" : "deprecated",
"valueCode" : "2.9"
},
{
"code" : "status",
"valueCode" : "A"
}]
},
{
"id" : "1080",
"code" : "XRC",
"display" : "Cineradiograph",
"definition" : "Cineradiograph",
"designation" : [{
"language" : "de",
"use" : {
"system" : "http://terminology.hl7.org/CodeSystem/hl7TermMaintInfra",
"code" : "preferredForLanguage"
},
"value" : "RÃ¶ntgenkinematographie"
}],
"property" : [{
"code" : "status",
"valueCode" : "A"
}]
}]
}

Copilot · 2025-10-28T19:50:15Z

@copilot Here's a copy of the CodeSystem that you couldn't find: {
"resourceType" : "CodeSystem",
"id" : "v2-0074",...

The CodeSystem JSON appears to be truncated in the comment. Could you provide the complete CodeSystem definition for v2-0074, or let me know where I should place this file in the test data? Once I have the complete CodeSystem, I can update the test to use the original diagnostic-service-sections ValueSet as requested.

alexzautke · 2025-10-28T19:53:19Z

CodeSystem-v2-0074.json
@copilot Here's the full JSON representation of the CodeSystem.

Changed test to use the original ValueSet from the bug report. Test passes in R4 but fails in R4B and R5 due to missing v2-0074 CodeSystem in those specification packages. Co-authored-by: alexzautke <[email protected]>

Copilot · 2025-10-28T20:02:04Z

CodeSystem-v2-0074.json
@copilot Here's the full JSON representation of the CodeSystem.

Updated in f70d49b to use diagnostic-service-sections as requested.

Test currently passes in R4 but fails in R4B and R5 with "The ValueSet expander cannot find codesystem 'http://terminology.hl7.org/CodeSystem/v2-0074'".

You mentioned the CodeSystem should be part of the specification.zip in R5 - could you verify if the test specification packages being loaded include this CodeSystem? The standard ZipSource.CreateValidationSource() resolver doesn't seem to find it in R4B/R5.

alexzautke · 2025-10-28T20:26:43Z

@copilot It's ok to use http://hl7.org/fhir/ValueSet/item-type, this is easier

Changed back to using http://hl7.org/fhir/ValueSet/item-type as confirmed by reviewer. This ValueSet works consistently across R4, R4B, and R5, and includes properties in R5 for proper testing of the Property field fix. Co-authored-by: alexzautke <[email protected]>

Copilot · 2025-10-28T20:32:47Z

@copilot It's ok to use http://hl7.org/fhir/ValueSet/item-type, this is easier

Reverted to item-type in b3f2ff3. All tests now pass across R4, R4B, and R5 with proper Property field verification in R5.

Initial plan

5548809

Copilot AI assigned Copilot and alexzautke Oct 24, 2025

Copilot started work on behalf of alexzautke October 24, 2025 17:48 View session

Copilot AI changed the title ~~[WIP] Fix NullReferenceException in ValueSet serialization~~ Fix NullReferenceException during ValueSet serialization in R4/R4B Oct 24, 2025

Copilot AI requested a review from alexzautke October 24, 2025 18:05

Copilot finished work on behalf of alexzautke October 24, 2025 18:05

brendankowitz reviewed Oct 27, 2025

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src/Hl7.Fhir.Shims.Base/Specification/Terminology/ValueSetExpander.cs Outdated Show resolved Hide resolved

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Co-authored-by: Brendan Kowitz <[email protected]>

alexzautke requested a review from ewoutkramer October 28, 2025 09:56

alexzautke marked this pull request as ready for review October 28, 2025 12:29

Merge branch 'develop' into copilot/fix-null-reference-exception

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ewoutkramer closed this Oct 28, 2025

alexzautke reopened this Oct 28, 2025

Merge branch 'develop' into copilot/fix-null-reference-exception

841632b

alexzautke enabled auto-merge October 28, 2025 18:13

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Copilot started work on behalf of alexzautke October 28, 2025 19:14 View session

Fix build error: Update test to use ToJson instead of ToJsonAsync

c8f696d

The serialization API changed after the merge with develop branch. Updated the test to use the new synchronous ToJson() method instead of the obsolete ToJsonAsync() method. Co-authored-by: alexzautke <[email protected]>

Copilot AI dismissed ewoutkramer’s stale review via c8f696d October 28, 2025 19:22

Copilot finished work on behalf of alexzautke October 28, 2025 19:24

alexzautke requested a review from ewoutkramer October 28, 2025 19:36

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Copilot finished work on behalf of alexzautke October 28, 2025 19:48

Copilot started work on behalf of alexzautke October 28, 2025 19:49 View session

Copilot finished work on behalf of alexzautke October 28, 2025 19:50

Copilot started work on behalf of alexzautke October 28, 2025 19:53 View session

Update test to use diagnostic-service-sections ValueSet

f70d49b

Changed test to use the original ValueSet from the bug report. Test passes in R4 but fails in R4B and R5 due to missing v2-0074 CodeSystem in those specification packages. Co-authored-by: alexzautke <[email protected]>

Copilot finished work on behalf of alexzautke October 28, 2025 20:02

Copilot started work on behalf of alexzautke October 28, 2025 20:27 View session

Copilot finished work on behalf of alexzautke October 28, 2025 20:33

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Fix NullReferenceException during ValueSet serialization in R4/R4B #3328

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Fix NullReferenceException during ValueSet serialization in R4/R4B #3328

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Copilot AI commented Oct 24, 2025 •

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