> ## Documentation Index
> Fetch the complete documentation index at: https://launchdarkly.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# OpenFeature provider for .NET (server-side) SDK

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<View title="Federal docs" />

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

<Note>
  **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:

  <table className="fern-table">
    <thead>
      <tr>
        <th>Resource</th>
        <th>Location</th>
      </tr>
    </thead>

    <tbody>
      <tr>
        <td>OpenFeature Provider API documentation</td>
        <td>[Provider API docs](https://launchdarkly.github.io/openfeature-dotnet-server/)</td>
      </tr>

      <tr>
        <td>GitHub repository</td>
        <td>[openfeature-dotnet-server](https://github.com/launchdarkly/openfeature-dotnet-server)</td>
      </tr>

      <tr>
        <td>Sample application</td>
        <td>[Sample OpenFeature .NET provider application](https://github.com/launchdarkly/hello-openfeature-dotnet-server)</td>
      </tr>

      <tr>
        <td>Published module</td>
        <td>[NuGet](https://www.nuget.org/packages/LaunchDarkly.OpenFeature.ServerProvider)</td>
      </tr>
    </tbody>
  </table>
</Note>

## 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.

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

### Version compatibility

The LaunchDarkly OpenFeature provider for the .NET (server-side) SDK is compatible with the [OpenFeature .NET SDK v2.0](https://openfeature.dev/docs/reference/technologies/server/dotnet).

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

## Install the provider

First, add the LaunchDarkly and OpenFeature packages:

<CodeGroup>
  ```bash title="Shell" lines wrap theme={null}
  dotnet add package LaunchDarkly.ServerSdk
  dotnet add package LaunchDarkly.OpenFeature.ServerProvider
  dotnet add package OpenFeature
  ```
</CodeGroup>

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

<CodeGroup>
  ```csharp title="LaunchDarkly .NET (server-side) provider" lines wrap theme={null}
  using LaunchDarkly.OpenFeature.ServerProvider;
  using LaunchDarkly.Sdk.Server;
  using OpenFeature.Model;
  ```
</CodeGroup>

## Initialize the provider

After you install and import the provider, create a single, shared instance of [`Provider`](https://launchdarkly.github.io/openfeature-dotnet-server/api/LaunchDarkly.OpenFeature.ServerProvider.Provider.html#LaunchDarkly_OpenFeature_ServerProvider_Provider__ctor_LaunchDarkly_Sdk_Server_Configuration_). Specify your SDK key here to authorize your application to connect to a particular environment within LaunchDarkly.

Here's how:

<CodeGroup>
  ```csharp title="C#" lines wrap theme={null}
  var config = Configuration.Builder("YOUR_SDK_KEY")
      .StartWaitTime(TimeSpan.FromSeconds(10))
      .Build();

  var provider = new Provider(config);

  await OpenFeature.Api.Instance.SetProviderAsync(provider);

  var client = OpenFeature.Api.Instance.GetClient();
  ```
</CodeGroup>

The configuration options are from the LaunchDarkly .NET (server-side) SDK. To learn more about the configuration options available, read [SDK configuration](/docs/sdk/features/config#net-server-side).

<Note>
  **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 on the **SDK keys** page under **Settings**. To learn more about key types, read [Keys](/docs/sdk/concepts/client-side-server-side#keys-and-credentials).
</Note>

## Construct a context

A [context](/docs/home/getting-started/vocabulary#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](https://openfeature.dev/docs/reference/concepts/evaluation-context).

In the LaunchDarkly provider, contexts:

* always have a particular [context kind](/docs/home/getting-started/vocabulary#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:

<CodeGroup>
  ```csharp title="Example user context" lines wrap theme={null}
  var context = EvaluationContext.Builder()
  .Set("targetingKey", "example-user-key") // Could also use "key" instead of "targetingKey".
  .Build();
  ```

  ```csharp title="Example organization context" lines wrap theme={null}
  var context = EvaluationContext.Builder()
  .Set("kind", "organization")
  .Set("targetingKey", "example-organization-key") // Could also use "key" instead of "targetingKey".
  .Build();
  ```
</CodeGroup>

For additional examples, read [OpenFeature specific considerations](https://github.com/launchdarkly/openfeature-dotnet-server?tab=readme-ov-file#openfeature-specific-considerations) in the provider GitHub repository.

## Evaluate a context

To evaluate feature flags for a context, use the OpenFeature [Evaluation API](https://openfeature.dev/docs/reference/concepts/evaluation-api). For example:

<CodeGroup>
  ```csharp title="Evaluate a context" lines wrap theme={null}
  var flagValue = await client.GetBooleanValueAsync("example-flag-key", false, context);
  ```
</CodeGroup>

## Access the LaunchDarkly client

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

To access the `LdClient`, use `GetClient()`:

<CodeGroup>
  ```csharp title="C#" lines wrap theme={null}
  var ldClient = provider.GetClient();
  ```
</CodeGroup>