FhirSerializer.SerializeResourceToXml not serializing Extensions (old version of Hl7.Net library)

[Benson Lott]

I am calling

string fhirString = FhirSerializer.SerializeResourceToXml(fhirBundle, Hl7.Fhir.Rest.SummaryType.True);

in the `fhirBundle` object, there is a Communication resource entry which I have added extensions to, like so:

            communication.AddExtension(Constants.ThxExtReplyTo,
                new ResourceReference()
                {
                    Reference = Constants.CdxPractitionerUrl + senderPractId,
                    Extension = new List<Extension>()
                    {
                        // this is the on-behalf-of sub extension
                        new Extension()
                        {
                            Url = Constants.ThxExtOnBehalfof,
                            Value = new ResourceReference()
                            {
                                Reference = Constants.CdxOrganizationUrl + senderOrgId
                            }
                        }
                    }
                }
            );

When debugging, I can see the fhirBundle/Communication entry.Resource does contain the extensions, but after serialization, they are not in the resulting XML.

In contrast, in the Communication/recipient element, I am able to add and extension and it works -- for example:

                var recipRef = new ResourceReference();
                if (recip.providerType.Equals("Primary"))
                {
                    recipRef.AddExtension(Constants.ThxExtPrimaryRecipient, new FhirBoolean(true));
                }
                recipRef.AddExtension(Constants.ThxExtOnBehalfof, new ResourceReference()
                {
                    //Url = new Uri(Constants.ThxExtOnBehalfof),
                    Reference = Constants.CdxOrganizationUrl + recip.providerLocation.GetLocationKey()
                    //Value = new FhirString(Constants.CdxOrganizationUrl + recip.providerLocation.GetLocationKey())
                });
                communication.Recipient.Add(recipRef);

This is an OLD version of the .Net library, so I realize it's done a little differently now, but is there some knowledge out there to indicate what I might be doing wrong. Extensions ARE working in other places, but in many I cannot get them to work. I have no choice in teh version that we are using since this is beyond my control.

Here is the complete Communication XML that results from using the code above:

<Communication>

<id value="495e2bc8-3d9f-47c2-a4c8-a59650dd9d0a" />

<meta>

<security>

<system value="http://hl7.org/fhir/v3/Confidentiality" />

<code value="R" />

<display value="restricted" />

</security>

<tag>

<system value="http://hl7.org/fhir/v3/ObservationValue" />

<code value="SUBSETTED" />

</tag>

</meta>

<identifier>

<system value="urn:ietf:rfc3986" />

<value value="urn:uuid:495e2bc8-3d9f-47c2-a4c8-a59650dd9d0a" />

</identifier>

<category>

<coding>

<system value="http://mydomain.com/fhir/CodeSystem/mydomain-md-communication-category" />

<code value="consult" />

</coding>

</category>

<recipient>

<extension url="http://mydomain.com/fhir/StructureDefinition/ext-communication-recipient-primary">

<valueBoolean value="true" />

</extension>

<extension url="http://mydomain.com/fhir/StructureDefinition/ext-reference-on-behalf-of">

<valueReference>

<reference value="https://services.bccdx.ca/fhir/Organization/CDX000396" />

</valueReference>

</extension>

</recipient>

<payload>

<contentAttachment>

<contentType value="application/pdf" />

<url value="f634504b-79a2-e911-a96d-0050568c55a6" />

<size value="84110" />

<title value=".pdf" />

</contentAttachment>

</payload>

<status value="in-progress" />

<sent value="2019-07-10T15:14:46-07:00" />

<subject>

<reference value="Patient/1a49fa2d-6a76-4862-9cb9-694d173276df" />

</subject>

</Communication>

[Benson Lott]

I figured out what's going on: I needed to user Hl7.Fhir.Rest.SummaryType.False However, this introduced another problem as I'm getting "Data root element is invalid". I imagine that means my Entry Components are not valid or missing some data. I was able to strip them out one by one and find the one that does serialize, but I can't see the difference.

Any clues on how to tell what might be missing or broken from the Serializer's perspective?