.NET Server SDK

statsig-io/dotnet-sdk

Installation

The package is hosted on Nuget. You can either install it from your Visual Studio's Nuget package manager, or through the NuGet CLI:

nuget install Statsig

Initialize the SDK

After installation, you will need to initialize the SDK using a Server Secret Key from the statsig console.

info

Do NOT embed your Server Secret Key in client-side applications, or expose it in any external-facing documents. However, if you accidentally expose it, you can create a new one in the Statsig console.

There is also an optional parameter named options that allows you to pass in a StatsigOptions to customize the SDK.

using Statsig;
using Statsig.Server;

await StatsigServer.Initialize(
    "server-secret-key",
    // optionally customize the SDKs configuration via StatsigOptions
    new StatsigOptions(
        environment: new StatsigEnvironment(EnvironmentTier.Development)
    )
);

initialize will perform a network request. After initialize completes, virtually all SDK operations will be synchronous (See Evaluating Feature Gates in the Statsig SDK). The SDK will fetch updates from Statsig in the background, independently of your API calls.

Working with the SDK

Checking a Feature Flag/Gate

Now that your SDK is initialized, let's fetch a Feature Gate. Feature Gates can be used to create logic branches in code that can be rolled out to different users from the Statsig Console. Gates are always CLOSED or OFF (think return false;) by default.

From this point on, all APIs will require you to specify the user (see Statsig user) associated with the request. For example, check a gate for a certain user like this:

var user = new StatsigUser { UserID = "some_user_id", Email = "user@email.com" };
var useNewFeature = await StatsigServer.CheckGate(user, "use_new_feature");
if (useNewFeature)
{
  // Gate is on, enable new feature
}
else
{
  // Gate is off
}

Reading a Dynamic Config

Feature Gates can be very useful for simple on/off switches, with optional but advanced user targeting. However, if you want to be able send a different set of values (strings, numbers, and etc.) to your clients based on specific user attributes, e.g. country, Dynamic Configs can help you with that. The API is very similar to Feature Gates, but you get an entire json object you can configure on the server and you can fetch typed parameters from it. For example:

var config = await StatsigServer.GetConfig(user, "awesome_product_details");

// The 2nd parameter is the default value to be used in case the given parameter name does not exist on
// the Dynamic Config object. This can happen when there is a typo, or when the user is offline and the
// value has not been cached on the client.
string itemName = config.Get<string>("product_name", "Awesome Product v1");
double price = config.Get<double>("price", 10.0);
bool shouldDiscount = config.Get<bool>("discount", false);

Getting an Layer/Experiment

Then we have Layers/Experiments, which you can use to run A/B/n experiments. We offer two APIs, but we recommend the use of layers to enable quicker iterations with parameter reuse.

// Values via getLayer

var layer = Statsig.GetLayer(user, "user_promo_experiments");
var promoTitle = layer.Get("title", "Welcome to Statsig!");
var discount = layer.Get("discount", 0.1);

// or, via getExperiment

var titleExperiment = Statsig.GetExperiment(user, "new_user_promo_title");
var priceExperiment = Statsig.GetExperiment(user, "new_user_promo_price");

var promoTitle = titleExperiment.Get("title", "Welcome to Statsig!");
var discount = priceExperiment.Get("discount", 0.1);

...

double price = msrp * (1 - discount);

Asynchronous APIs

We mentioned earlier that after calling initialize most SDK APIs would run synchronously, so why are getConfig and checkGate asynchronous?

The main reason is that older versions of the SDK might not know how to interpret new types of gate conditions. In such cases the SDK will make an asynchronous call to our servers to fetch the result of a check. This can be resolved by upgrading the SDK, and we will warn you if this happens.

For more details, read our blog post about SDK evaluations. If you have any questions, please ask them in our Feedback Repository.

Logging an Event

Now that you have a Feature Gate or an Experiment set up, you may want to track some custom events and see how your new features or different experiment groups affect these events. This is super easy with Statsig - simply call the Log Event API and specify the user and event name to log; you additionally provide some value and/or an object of metadata to be logged together with the event:

StatsigServer.LogEvent(
  user,
  "add_to_cart",
  "SKU_12345",
  new Dictionary<string, string>() {
    { "price", "9.99" },
    { "item_name", "diet_coke_48_pack" }
  }
);

Learn more about identifying users, group analytics, and best practices for logging events in the logging events guide.

Retrieving Feature Gate Metadata

In certain scenarios, you may need more information about a gate evaluation than just a boolean value. For additional metadata about the evaluation, use the Get Feature Gate API, which returns a FeatureGate object

Statsig User

When calling APIs that require a user, you should pass as much information as possible in order to take advantage of advanced gate and config conditions (like country or OS/browser level checks), and correctly measure impact of your experiments on your metrics/events. The userID field is required because it's needed to provide a consistent experience for a given user (click here to understand further why it's important to always provide a userID).

Besides userID, we also have email, ip, userAgent, country, locale and appVersion as top-level fields on StatsigUser. In addition, you can pass any key-value pairs in an object/dictionary to the custom field and be able to create targeting based on them.

Note that while typing is lenient on the StatsigUser object to allow you to pass in numbers, strings, arrays, objects, and potentially even enums or classes, the evaluation operators will only be able to operate on primitive types - mostly strings and numbers. While we attempt to smartly cast custom field types to match the operator, we cannot guarantee evaluation results for other types. For example, setting an array as a custom field will only ever be compared as a string - there is no operator to match a value in that array.

Private Attributes

Have sensitive user PII data that should not be logged? No problem, we have a solution for it! On the StatsigUser object we also have a field called privateAttributes, which is a simple object/dictionary that you can use to set private user attributes. Any attribute set in privateAttributes will only be used for evaluation/targeting, and removed from any logs before they are sent to Statsig server.

For example, if you have feature gates that should only pass for users with emails ending in "@statsig.com", but do not want to log your users' email addresses to Statsig, you can simply add the key-value pair { email: "my_user@statsig.com" } to privateAttributes on the user and that's it!

Statsig Options

Initialize() takes an optional parameter options in addition to sdkKey and user that you can provide to customize the Statsig client. Here are the current options and we are always adding more to the list:

• apiUrlBase: string, default null
  • Allows you to override the API url base path, enabling custom/internal proxy forwarding.
• environment: StatsigEnvironment, default null
  • An object you can use to set environment variables that apply to all of your users in the same session and will be used for targeting purposes.
  • The most common usage is to set the environment tier (EnvironmentTier), e.g. new StatsigEnvironment(EnvironmentTier.Staging), and have feature gates pass/fail for specific environments.
• RulesetsSyncInterval: double, default 10
  • Use this to override how often you want the SDK to poll Statsig backend for changes on the rulesets.
• IDListsSyncInterval: double, default 60
  • Use this to override how often you want the SDK to poll Statsig backend for changes on the ID Lists.
• LocalMode: bool, default false
  • Pass true to this option to turn on Local Mode for the SDK, which will stop the SDK from issuing any network requests and make it only operate with only local overrides (If supported) and cache.
    Note: Since no network requests will be made, a dummy SDK key starting with "secret-" can be used. (eg "secret-key")
• DataStore: IDataStore, default null
  • A class that extends IDataStore. Can be used to provide values from a common data store (like Redis) to initialize the Statsig SDK.

Shutting Statsig Down

Because we batch and periodically flush events, some events may not have been sent when your app/server shuts down.

To make sure all logged events are properly flushed, you should tell Statsig to shutdown when your app/server is closing:

StatsigServer.Shutdown();

Data Store

If you would like to implement your own caching logic, or have finer control over the network requests sent to Statsig, you can implement your own DataStore. You can provide a DataStore via StatsigOptions.DataStore.

If you would like to know more about how Data Stores work, you can read more about the concept here.

Data Store Interface

You can write you own custom Data Stores that implement the following interface:

public interface IDataStore
  {
    bool SupportsPollingUpdates(string key);

    Task Init();

    Task Shutdown();

    Task<string?> Get(string key);

    Task Set(string key, string value);
  }

Example Implementation

The .NET Redis DataStore can be found as a NuGet package here: https://www.nuget.org/packages/StatsigRedis. It leverages the standard StackExchange.Redis package.

public class RedisDataStore : IDataStore
{
  public bool AllowConfigSpecPolling = false;

  public RedisDataStore(IDatabase database){}

  public RedisDataStore(string host, int port, string password){}
}

Local Overrides v1.21.0+

If you want to locally override gates/configs/experiments/layers, there are a set of override APIs as follows. Coupling this with StatsigOptions.localMode can be useful when writing unit tests.

These can be used to set an override for a specific user, or for all users (by not providing a specific user ID). Experiments/Autotune are overridden with the overrideConfig API.

# Adding gate overrides
StatsigServer.OverrideGate("a_gate_name", true, "a_user_id")

# Adding config overrides
StatsigServer.OverrideConfig("a_config_name", {"key" => "value"}, "a_user_id")

# Adding layer overrides
StatsigServer.OverrideLayer("a_layer_name", {"key" => "value"}, "a_user_id")

note

1. These only apply locally - they do not update definitions in the Statsig console or elsewhere.
2. The local override API is not designed to be a full mock. They are only a convenient way to override the value of the gate/config/etc.

Multiple Statsig SDK Instances

Our documentation up to this point guides you through setting up your Statsig integration via the singleton Statsig.

There are cases where you may need to create multiple instances of the Statsig SDK. Each SDK supports this as well - the Statsig singleton wraps a single instance of the SDK that you can instantiate. NOTE: currently all sdk instances will use the same keys when interacting with a Data Store/Data Adapter. You will not be able to isolate multiple instances of the sdk in your data store.

All top level static methods from the singleton carry over as instance methods. To create an instance of the Statsig sdk:

ServerDriver sdkInstance = new ServerDriver(secretKey, options);
await serverDriver.Initialize().ConfigureAwait(false);

FAQ

How do I run experiments for logged out users?

See the guide on device level experiments

Reference

Type StatsigUser

public class StatsigUser
{
    public string? UserID
    public string? Email
    public string? IPAddress
    public string? UserAgent
    public string? Country
    public string? Locale
    public string? AppVersion

    public StatsigUser()

    public void AddCustomProperty(string key, object value)

    public void AddPrivateAttribute(string key, object value)

    public void AddCustomID(string idType, string value)
}

Type StatsigOptions

// Shared with the .NET Client SDK
public class StatsigOptions
{
    public string ApiUrlBase { get; }
    public StatsigEnvironment StatsigEnvironment { get; }
    public string? PersistentStorageFolder { get; set; }
    public double RulesetsSyncInterval = 60;
    public double IDListsSyncInterval = 60;
    public int ClientRequestTimeoutMs = 0;

    private Dictionary<string, string> _additionalHeaders;
    private Func<IIDStore>? _idStoreFactory = null;

    public StatsigOptions(string? apiUrlBase = null, StatsigEnvironment? environment = null)
}

// Server-specific options
public class StatsigServerOptions : StatsigOptions
{
    public bool LocalMode;

    public IDataStore DataStore;

    public StatsigServerOptions(string? apiUrlBase = null, StatsigEnvironment? environment = null) : base(
        apiUrlBase, environment)
}