.NET SDK reference (client-side)

Overview

This topic documents how to get started with the client-side .NET SDK, and links to reference information on all of the supported features.

Get started

After you complete the Get started process, follow these instructions to start using the LaunchDarkly SDK in your application:

• Understand version compatibility
• Install the SDK
• Initialize the client
• Evaluate a flag

Understand version compatibility

Starting with version 5, the .NET (client-side) SDK supports Microsoft's .NET 7 and MAUI.

The LaunchDarkly .NET (client-side) SDK is compatible with Android version 5.0 and higher and with iOS version 11.0 and higher. It is also compatible with any other platform that supports .NET Standard version 2.0 or higher, although the .NET Standard version lacks some mobile-specific features such as detecting network connectivity.

If you use Xamarin, you cannot use version 5 of the LaunchDarkly .NET (client-side) SDK. You must migrate to MAUI to continue using the LaunchDarkly SDK. To learn more about migrating, read Microsoft's documentation on how to Upgrade from Xamarin to .NET.

Install the SDK

To start using the client-side .NET SDK:

Install-Package LaunchDarkly.ClientSdk
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Next, import the LaunchDarkly packages in your application code:

using LaunchDarkly.Sdk;
using LaunchDarkly.Sdk.Client;
// LaunchDarkly.Sdk defines general types like Context, which are also used in the server-side .NET SDK.
// LaunchDarkly.Sdk.Client defines the LdClient and Configuration types for the client-side .NET SDK.
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Initialize the client

After you install the dependency, initialize the LaunchDarkly client by creating a single, shared instance of LdClient. To create a client instance, you need your environment's mobile key. This authorizes your application to connect to a particular environment within LaunchDarkly.

We recommend calling the client initialization method with a timeout of 0-5 seconds. This means your application blocks for a short period of time, until the SDK retrieves the latest feature flags from LaunchDarkly. We recommend that you do not set the timeout parameter for more than five seconds.

Here's how:

var context = Context.New("context-key-123abc");
var timeSpan = TimeSpan.FromSeconds(5);
client = LdClient.Init("mobile-key-123abc", ConfigurationBuilder.AutoEnvAttributes.Enabled, context, timeSpan);
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You can also initialize the SDK asynchronously. As with the Init method, we recommend that you do not set the timeout parameter for more than five seconds.

Older versions of the SDK allow you to initialize the SDK asynchronously without a timeout option. We do not recommend this because initializing without a timeout option will cause your app never to load if there is a connectivity problem.

To initialize asynchronously:

Context context = Context.New("context-key-123abc");
var timeSpan = TimeSpan.FromSeconds(5);
client = await LdClient.InitAsync("mobile-key-123abc", ConfigurationBuilder.AutoEnvAttributes.Enabled, context, timeSpan);
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For a complete list of the specific LdClient configuration options available in this SDK, read Configuration.

Evaluate a flag

After you create the client, you can use it to check which variation a particular context will receive for a given feature flag.

Here's how:

bool showFeature = client.BoolVariation("flag-key-123abc", false);
if (showFeature) {
    // Application code to show the feature
}
else {
    // The code to run if the feature is off
}
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Using the Relay Proxy

You can configure the client-side .NET SDK to connect to the Relay Proxy as follows:

var config = Configuration
    .Builder("mobile-key-123abc", AutoEnvAttributes.Enabled)
    .ServiceEndpoints(
        Components.ServiceEndpoints().RelayProxy("YOUR_RELAY_URI")
    )
    .Build();
LdClient client = LdClient.Init(config);
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Shut down the client

Shut down the client when your application terminates. To learn more, read Shutting down.

Data collection

To learn more about data collection within this SDK and implications on submissions to the Apple App Store, read the Apple App Store data collection policy.

Supported features

This SDK supports the following features:

• Anonymous contexts and users
• Automatic environment attributes
• Configuration, including
  • Application metadata configuration
  • Service endpoint configuration
• Context configuration
• Evaluating flags
• Flag evaluation reasons
• Flushing events
• Getting all flags
• Identifying and changing contexts
• Logging configuration
• Monitoring SDK status
• Offline mode
• Private attributes
• Relay Proxy configuration, using proxy mode
• Sending custom events
• Shutting down
• Subscribing to flag changes
• Test data sources
• Web proxy configuration