## Set up the SDK

{% steps %}
{% step title="Install the SDK" %}
The package is hosted on [Nuget](https://www.nuget.org/packages/Statsig/). Install it from your Visual Studio's Nuget package manager, or through the NuGet CLI:

```shell
nuget install Statsig
```
{% /step %}

{% step title="Initialize the SDK" %}
Next, initialize the SDK with a client SDK key from the ["API Keys" tab on the Statsig console](https://console.statsig.com/api_keys). These keys are safe to embed in a client application.

Along with the key, pass in a [User Object](#statsig-user) with the attributes you'd like to target later on in a gate or experiment.

```csharp
using Statsig;
using Statsig.Client;

await StatsigClient.Initialize(
    "client-sdk-key",
    new StatsigUser { UserID = "some_user_id", Email = "user@email.com" },
    new StatsigOptions(new StatsigEnvironment(EnvironmentTier.Development)) // optional, use when needed to customize certain behaviors
);
```
{% /step %}
{% /steps %}

## Use the SDK

### Checking a Feature Flag/Gate

Now that your SDK is initialized, let's check a [**Feature Gate**](/feature-flags/overview). 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.

```csharp
if (StatsigClient.CheckGate("new_homepage_design"))
{
  // Gate is on, show new home page
}
else
{
  // Gate is off, show old home page
}
```

### Reading a Dynamic Config

Feature Gates are useful for simple on/off switches with optional advanced user targeting. To send a different set of values (strings, numbers, etc.) to clients based on specific user attributes such as country, use **Dynamic Configs**. The API is similar to Feature Gates, but you get a complete JSON object you can configure on the server and fetch typed parameters from it. For example:

```csharp
DynamicConfig config = StatsigClient.GetConfig("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 a Layer/Experiment

**Layers/Experiments** let you run A/B/n experiments. Two APIs are available, but Statsig recommends [layers](/experiments/layers-overview) for quicker iterations with parameter reuse.

```csharp
// Values via getLayer

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

// or, via getExperiment

DynamicConfig  titleExperiment = StatsigClient.GetExperiment("new_user_promo_title");
DynamicConfig  priceExperiment = StatsigClient.GetExperiment("new_user_promo_price");

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

...

double price = msrp * (1 - discount);
```

### Logging an Event

After setting up a Feature Gate or Experiment, you may want to track custom events to see how new features or experiment groups affect those events. Call the Log Event API for the event. You can also provide a value and metadata object to be logged with the event:

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

## Statsig User

You need to provide a StatsigUser object to check/get your configurations. Pass as much
information as possible to take advantage of advanced gate and config conditions.

Most of the time, the `userID` field is needed to provide a consistent experience for a given
user (refer to [logged-out experiments](/guides/first-device-level-experiment) to understand how to correctly run experiments for logged-out
users).

Besides `userID`, Statsig also supports `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 create targeting based on them.

After the user logs in or their attributes change, call `updateUser` with the updated `userID` and any other updated user attributes:

```csharp
// if you want to update the existing user, or change to a different user, call updateUser

await StatsigClient.UpdateUser(
    new StatsigUser { UserID = "new_user_id", Email = "new_user@email.com" },
);
```

### Private Attributes

To prevent sensitive user PII from being logged, use the `privateAttributes` field on the StatsigUser object. Statsig uses attributes set in `privateAttributes` only for evaluation and targeting, then removes them from any logs before sending them to the server.

For example, if you have feature gates that pass only for users with emails ending in "@statsig.com" but don't want to log your users' email addresses to Statsig, add the key-value pair `{ email: "my_user@statsig.com" }` to `privateAttributes` on the user.

## Statsig Options

`Initialize()` takes an optional parameter `options` in addition to `sdkKey` and `user` that you can provide to customize the Statsig client.

{% parameter name="environment" type="StatsigEnvironment" %}
Set environment variables that apply to all users in the session for targeting purposes.
Commonly used to set the environment tier, e.g. `new StatsigEnvironment(EnvironmentTier.Staging)`.
{% /parameter %}

{% parameter name="ClientRequestTimeoutMs" type="int" %}
Maximum milliseconds to wait for `/initialize` before proceeding with cached/default values.
{% /parameter %}

{% parameter name="PersistentStorageFolder" type="string" %}
Directory path for persistent storage of cached values and logs.
{% /parameter %}

## Shutting Statsig Down

The SDK keeps event logs in the client cache and flushes them periodically to save data and battery usage. Because of this, some events may not have been flushed when your app shuts down.

To ensure all logged events are flushed or saved locally, shut down Statsig when your app is closing:

```csharp
StatsigClient.Shutdown();
```

## FAQs

#### How do I run experiments for logged out users?

Refer to [Device-level experiments](/sdks/user#device-level-experiments).