I have two types Person and Honorific with a 0..1 to Many relationship between them. I am using queryOptions.request.SetSelectExpandClass to support expand and it works perfectly to expand Honorific when there is an Honorific.
When there is no Honorific I need the Json payload to include Honorific=(null). In that situation I return a null from TryGetPropertyValue but the Json serializer completely omits any reference to Honorific where it should insert Honorif=(null). Any ideas on how to achieve this? Thanks!
I don't think OData allows that the value of a collection is null.
A null collection is handled by WebAPI which will ignore a null collection during serialization.
I think it is a bug in WebAPI and a null collection should be treated as an empty collection during serialization.
Check the source code of WebAPI blow:
For OData V3:
\src\System.Web.Http.OData\OData\Formatter\Serialization\ODataEntityTypeSerializer.cs:WriteExpandedNavigationPropertyFor OData V4:
\src\System.Web.OData\OData\Formatter\Serialization\ODataEntityTypeSerializer.cs:WriteExpandedNavigationProperty