How to determine if search response had either zero or too many matches

[djames-octave]

I am implementing a patient search using the Task<Bundle?> SearchAsync<TResource>(SearchParams q, CancellationToken? ct = null) overload with a resource type of Patient. When the search results in either zero or too many matches a null response is returned. This looks to be due to each scenario returning a Http 200 response, so an exception isn't being raised, with an OperationOutcome response type which then isn't deserialising to the Patient type requested. To note, I am currently testing against the Personal Demographics Service sandbox.

Is there a way to handle this differently in my implementation so I can determine whether the response had zero matches or too many matches? The intention is to feedback to the user why no search results are being returned.

[mbaltus]

The sandbox is not responding 100% correctly according to the FHIR specs, since that says:

If the search fails (cannot be executed, not that there are no matches), the return value return value SHALL be a status code 4xx or 5xx with an OperationOutcome.

I've tried and can only do the mock calls on the sandbox, and their responses are completely fixed. On their actual servers they may respond as expected but I cannot test that. Might be worth it to reach out to them before you do a lot of extra work that is only relevant for the sandbox.

I could only reproduce one of your issues, where an OperationOutcome is returned with a 200 OK status, leading to a null from the SearchAsync. The call that results in a Bundle with 0 results does work correctly, since you get your Bundle from the call then.

You can check your FhirClient.LastBodyAsResource if you get a null from the SearchAsync call. This will contain that OperationOutcome which you can then check for its error message.