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Rapidly create and deploy powerful .NET applications that integrate with FHIR.

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LINQ to FHIR Data


LINQ offers versatile querying capabilities within the .NET Framework (v3.0+), offering a straightforward method for programmatic data access through CData ADO.NET Data Providers. In this article, we demonstrate the use of LINQ to retrieve information from the FHIR Data Provider.

This article illustrates using LINQ to access tables within the FHIR via the CData ADO.NET Data Provider for FHIR. To achieve this, we will use LINQ to Entity Framework, which facilitates the generation of connections and can be seamlessly employed with any CData ADO.NET Data Providers to access data through LINQ.

See the help documentation for a guide to setting up an EF 6 project to use the provider.

  1. In a new project in Visual Studio, right-click on the project and choose to add a new item. Add an ADO.NET Entity Data Model.
  2. Choose EF Designer from Database and click Next.
  3. Add a new Data Connection, and change your data source type to "CData FHIR Data Source".

  4. Enter your data source connection information.

    Set URL to the Service Base URL of the FHIR server. This is the address where the resources are defined in the FHIR server you would like to connect to. Set ConnectionType to a supported connection type. Set ContentType to the format of your documents. Set AuthScheme based on the authentication requirements for your FHIR server.

    Generic, Azure-based, AWS-based, and Google-based FHIR server implementations are supported.

    Sample Service Base URLs

    • Generic: http://my_fhir_server/r4b/
    • Azure: https://MY_AZURE_FHIR.azurehealthcareapis.com/
    • AWS: https://healthlake.REGION.amazonaws.com/datastore/DATASTORE_ID/r4/
    • Google: https://healthcare.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/datasets/DATASET_ID/fhirStores/FHIR_STORE_ID/fhir/

    Generic FHIR Instances

    The product supports connections to custom instances of FHIR. Authentication to custom FHIR servers is handled via OAuth (read more about OAuth in the Help documentation. Before you can connect to custom FHIR instances, you must set ConnectionType to Generic.

    Below is a typical connection string:

    URL=http://test.fhir.org/r4b/;ConnectionType=Generic;ContentType=JSON;AuthScheme=None;
  5. If saving your entity connection to App.Config, set an entity name. In this example we are setting FHIREntities as our entity connection in App.Config.
  6. Enter a model name and select any tables or views you would like to include in the model.

Using the entity you created, you can now perform select commands. For example:

FHIREntities context = new FHIREntities(); var patientQuery = from patient in context.Patient select patient; foreach (var result in patientQuery) { Console.WriteLine("{0} {1} ", result.Id, result.Id); }

See "LINQ and Entity Framework" chapter in the help documentation for example queries of the supported LINQ.