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OpenFeature provider for .NET (server-side) SDK

Read time: 3 minutes
Last edited: Jun 18, 2024


This topic documents how to get started with the LaunchDarkly OpenFeature provider for the .NET (server-side) SDK.

Provider quick links

LaunchDarkly's OpenFeature providers are open source. In addition to this reference guide, we provide source, API reference documentation, and a sample application:

OpenFeature Provider API documentationProvider API docs
GitHub repositoryopenfeature-dotnet-server
Sample applicationSample OpenFeature .NET provider application
Published moduleNuGet

Get started

The LaunchDarkly OpenFeature provider for the .NET (server-side) SDK is intended for use in multi-user systems such as web servers and application. It is not intended for use in desktop and embedded systems applications.

The provider is compatible with .NET 6.0+, .NET Framework 4.7.1+, and .NET Standard 2.0+.

Follow these instructions to start using the LaunchDarkly OpenFeature provider for the .NET (server-side) SDK in your application.

Install the provider

First, add the LaunchDarkly and OpenFeature packages:

dotnet add package LaunchDarkly.ServerSdk
dotnet add package LaunchDarkly.OpenFeature.ServerProvider
dotnet add package OpenFeature

Next, import the OpenFeature and LaunchDarkly namespaces in your application code:

using LaunchDarkly.OpenFeature.ServerProvider;
using LaunchDarkly.Sdk.Server;

Initialize the provider

After you install and import the provider, create a single, shared instance of Provider. Specify your SDK key here to authorize your application to connect to a particular environment within LaunchDarkly.

Here's how:

var config = Configuration.Builder("sdk-key-123abc")
var provider = new Provider(config);
await OpenFeature.Api.Instance.SetProviderAsync(provider);
var client = OpenFeature.Api.Instance.GetClient();

The configuration options are from the LaunchDarkly .NET (server-side) SDK. To learn more about the configuration options available, read Configuration.

The .NET provider uses an SDK key

The LaunchDarkly .NET (server-side) provider uses an SDK key. Keys are specific to each project and environment. They are available from the Environments list for each project. To learn more about key types, read Keys.

Construct a context

A context is a generalized way of referring to the people, services, machines, or other resources that encounter feature flags in your product. The OpenFeature specification calls these evaluation contexts.

In the LaunchDarkly provider, contexts:

  • always have a particular context kind. If you do not specify a kind, the provider treats the context as having a "user" kind. To specify a different kind, including a multi-context, you must include a kind attribute.
  • must have a targeting key. This is optional in the OpenFeature specification, but LaunchDarkly requires a key for evaluation. You can specify this using targetingKey, as in the OpenFeature specification, or key, which is the typical LaunchDarkly identifier for the targeting key.

Here are examples of a context:

var context = EvaluationContext.Builder()
.Set("targetingKey", "user-key-123abc") // Could also use "key" instead of "targetingKey".

For additional examples, read OpenFeature specific considerations in the provider GitHub repository.

Evaluate a context

To evaluate feature flags for a context, use the OpenFeature Evaluation API. For example:

var flagValue = await client.GetBooleanValue("flag-key-123abc", false, context);

Access the LaunchDarkly client

You may need access to the LdClient from within the LaunchDarkly .NET (server-side) SDK if you are working on use cases not supported by OpenFeature, such as migration flags or sending custom events.

To access the LdClient, use GetClient():

var ldClient = provider.GetClient()