Updating the error message during conditional reference

src/Microsoft.Health.Fhir.Core/Resources.resx

@@ -255,6 +255,10 @@
     <value>Given conditional reference '{0}' does not resolve to a resource.</value>
     <comment>{0} is the conditional reference parameter.</comment>
   </data>
+  <data name="InvalidConditionalReferenceToMultipleResources" xml:space="preserve">
+    <value>Given conditional reference '{0}' resolved to multiple resources.</value>
+    <comment>{0} is the conditional reference parameter.</comment>
+  </data>
   <data name="InvalidConditionalReferenceParameters" xml:space="preserve">
     <value>Resource type and query parameter must be present in a given request '{0}'.</value>
     <comment>{0} is the request url.</comment>
@@ -744,4 +748,4 @@
     <value>The FHIR Server ran out of memory while processing an export job. Please use the _maxCount parameter when requesting an export job to reduce the number of resources exported at one time. The count used in this job was {0}</value>
     <comment>'{0}' the value of _maxCount used for this export job.</comment>
   </data>
-</root>
+</root>

src/Microsoft.Health.Fhir.Shared.Core.UnitTests/Features/Resources/ResourceReferenceResolverTests.cs

@@ -108,10 +108,32 @@ public async Task GivenATransactionBundleWithConditionalReferences_WhenNotResolv
             var requestBundle = Samples.GetJsonSample("Bundle-TransactionWithConditionalReferenceInResourceBody");
             var bundle = requestBundle.ToPoco<Hl7.Fhir.Model.Bundle>();
 
+            IEnumerable<SearchResultEntry> searchResultEntries = Enumerable.Empty<SearchResultEntry>();
+
+            var expectedMessage = "Given conditional reference 'Patient?identifier=12345' does not resolve to a resource.";
+
+            var searchResult = new SearchResult(searchResultEntries, null, null, new Tuple<string, string>[0]);
+            _searchService.SearchAsync("Patient", Arg.Any<IReadOnlyList<Tuple<string, string>>>(), CancellationToken.None).Returns(searchResult);
+
+            var referenceIdDictionary = new Dictionary<string, (string resourceId, string resourceType)>();
+            foreach (var entry in bundle.Entry)
+            {
+                var requestUrl = (entry.Request != null) ? entry.Request.Url : null;
+                var exception = await Assert.ThrowsAsync<RequestNotValidException>(() => _referenceResolver.ResolveReferencesAsync(entry.Resource, referenceIdDictionary, requestUrl, CancellationToken.None));
+                Assert.Equal(exception.Message, expectedMessage);
+            }
+        }
+
+        [Fact]
+        public async Task GivenATransactionBundleWithConditionalReferences_WhenResolvedToMultipleResources_ThenRequestNotValidExceptionShouldBeThrown()
+        {
+            var requestBundle = Samples.GetJsonSample("Bundle-TransactionWithConditionalReferenceInResourceBody");
+            var bundle = requestBundle.ToPoco<Hl7.Fhir.Model.Bundle>();
+
             SearchResultEntry mockSearchEntry = GetMockSearchEntry("123", KnownResourceTypes.Patient);
             SearchResultEntry mockSearchEntry1 = GetMockSearchEntry("123", KnownResourceTypes.Patient);
 
-            var expectedMessage = "Given conditional reference 'Patient?identifier=12345' does not resolve to a resource.";
+            var expectedMessage = "Given conditional reference 'Patient?identifier=12345' resolved to multiple resources.";
 
             var searchResult = new SearchResult(new[] { mockSearchEntry, mockSearchEntry1 }, null, null, new Tuple<string, string>[0]);
             _searchService.SearchAsync("Patient", Arg.Any<IReadOnlyList<Tuple<string, string>>>(), CancellationToken.None).Returns(searchResult);

src/Microsoft.Health.Fhir.Shared.Core/Features/Resources/ResourceReferenceResolver.cs

@@ -70,10 +70,14 @@ public async Task ResolveReferencesAsync(Resource resource, IDictionary<string,
 
                         var results = await GetExistingResourceId(requestUrl, resourceType, conditionalQueries, cancellationToken);
 
-                        if (results == null || results.Count != 1)
+                        if (results == null || results.Count == 0)
                         {
                             throw new RequestNotValidException(string.Format(Core.Resources.InvalidConditionalReference, reference.Reference));
                         }
+                        else if (results.Count > 1)
+                        {
+                            throw new RequestNotValidException(string.Format(Core.Resources.InvalidConditionalReferenceToMultipleResources, reference.Reference));
+                        }
 
                         string resourceId = results.First().Resource.ResourceId;