R4

Introduction

This is an unofficial WebAPI controller implementation for exposing a HL7 FHIR on the Microsoft .NET (dotnet) platform. It even supports data compression handling out of the box

This library provides:

• An implementation of an ApiController for the R4 FHIR specification
• An interface for the System Service
• An interface for the Resource Service
• A partial example implementation of a fhir server CRUD that just writes files to C:\Temp\demoserver
• A unit test project that utilizes the FhirClient NuGet packages to test the example Service
• Support for both Owin (.NET 4.7+) and AspNetCore
• An extra FhirHttpClient assembly that is a partial drop in replacement for the v1.9.0 FhirClient class that uses the HttpClient internally for use in Azure Function Apps and other locations where high load causes issues with socket exhaustion

The library depends on several NuGet packages (notably):

• Core (NuGet packages starting with Hl7.Fhir.<version>) - contains the FhirClient, resource object models and parsers
• Specification (NuGet packages starting with Hl7.Fhir.Specification.<version>) - functionality to work with the specification metadata and validation
• FhirPath (NuGet package Hl7.FhirPath) - the FhirPath evaluator, used by the Core and Specification assemblies
• Support (NuGet package Hl7.Fhir.Support) - a library with interfaces, abstractions and utility methods that are used by the other packages
• Owin

IMPORTANT Once things settle in, the HL7.Fhir.WebApi.R4 project will be created into a NuGet package. Before installing one of the NuGet packages (or clone the repo) it is important to understand that HL7 has published several updates of the FHIR specification, each with breaking changes - so you need to ensure you use the version that is right for you:

• R4 (published December 2019) latest release, support by this library.
• STU3 (published March 2017) increasing use, supported by this library - though not published as yet, and may not publish
• DSTU2 (published October 2015) in widespread use, not planning to supported by this library.

Getting Started

To create your own server, copy the Hl7.DemoFileSystemFhirServer example project, then start replacing the code in the DirectorySystemService and DirectoryResourceService classes. Depending on your implementation needs, you may have one or more Resource classes.

(Choose either the Owin if you have a .net 4.7+ project, or the aspnetcore project if using netcore 2.2, 3.0 or 3.1)

Support

TBD For questions and broader discussions, we use the .NET FHIR Implementers chat on Zulip.

Contributing

We are welcoming contributors!

If you want to participate in this project, we're using [Git Flow][nvie] for our branch management, so please submit your commits using pull requests no on the develop branches mentioned above!

GIT branching strategy

• NVIE
• Or see: Git workflow

History

This code in this project started life inside the Spark FHIR Server prior to the DSTU2 release.

At which point the Spark server only supported Mongo, and I needed SQL Server, so I forked the code and built a SQL version (which was closed source for the company I worked for). Over time the layer that implemented the API Facade was split into it's own package, and that is this code (no storage, just the Controller, Formatters, and plumbing for the base server)

Since then a lot of work has gone into maintaining this project, and refining it for the various versions of FHIR, and the dotnet framework.