Calling custom plugin for $lastn using Firely .Net SDK?

[EugOSullivan]

Hi All,

I'm having an issue calling a custom plugin for LastN I've made using the firely SDK and was wondering if anyone could give me some pointers. My FHIR server is using 2 custom plugins. Its using a facade plugin to point at our proprietary database and I've also added a custom LastN plugin to the pipeline to support calling $LastN on against Observations. This works fine for Http requests. however If I try to interact with the lastn operation via SDK I'm getting the issue described below:

Example:

var fhirClient = new FhirClient("http://localhost:4080");
var parameter = new Parameters();

parameter.Add("max", new FhirString("3"));
parameter.Add("patient", new FhirString("Patient/123456"));

// var result = await fhirClient.TypeOperationAsync<Observation>("lastn", parameter);
var result = fhirClient.TypeOperation<Observation>("lastn", parameter);

This hits the constructor of the ISearchRepository for my Firely facade plugin but doesn’t hit my custom Plugin.LastN constructor or method.

The IApplicationBuilder configuration for my LastN plugin is as below and the App instance json on the Server has supported type operation has $lastn.

public static IApplicationBuilder Configure(IApplicationBuilder builder)
        {
            // Register interactions
            builder
                .OnCustomInteraction(VonkInteraction.type_custom, "lastn")
                .AndResourceTypes(new[] { "Observation" })
                .AndMethod("GET")
                .HandleAsyncWith<LastN>((svc, context)
                    => svc.GetLastN(context));

            return builder;
        }

The error I get is

Exception has occurred: CLR/Hl7.Fhir.Rest.FhirOperationException
An unhandled exception of type 'Hl7.Fhir.Rest.FhirOperationException' occurred in Hl7.Fhir.Support.Poco.dll: 'Operation was unsuccessful, and returned status NotImplemented. OperationOutcome: Overall result: SUCCESS


[WARNING] Argument is not supported(further diagnostics: /Observation).'
   at Hl7.Fhir.Rest.TaskExtensions.WaitResult[T](Task`1 task)
   at Hl7.Fhir.Rest.BaseFhirClient.TypeOperation[TResource](String operationName, Parameters parameters, Boolean useGet)
   at Bundle_Builder.BundleViewer..ctor() in C:\**\FHIR\Bundle-Tester\Bundle-Builder\BundleViewer.cs:line 35
 

However if I do a Http Get such as below (RestClient in VsCode) the LastN plugin constructor and call method are being called and the endpoint is working as expected

get {{host}}/Observation/$lastn?subject:Patient._identifier=https://fhir.test.com/Id/pas-identifier|NN046351
Accept: {{contenttype}}
Content-Type: {{contenttype}}

Any tips as to what I'm doing wrong appreciated.
Regards

[EugOSullivan]

Apologies, after posting that I immediately spotted the mistake. Client.TypeOperation(Async) required useGET optional parameter to be true.

fhirClient.TypeOperationAsync<Observation>("lastn", parameter, true);