---
title: Example usage of the C# SDK
slug: feature-experimentation/docs/example-usage-csharp
docTags: 
createdAt: 2026-08-05T20:39:59.000Z
---

After installing the C# SDK, import the Optimizely library, get your project's datafile, and create a client. Use the client to evaluate flag rules like A/B tests and flag deliveries.

This example walks through the following three key steps:

1. Evaluate a flag with the key `product_sort` using the `Decide` method. This also sends a decision event to Optimizely to record that the user was exposed to the experiment.
2. Run code based on the flag result. The SDK evaluates your flag rules and determines which variation the user is in. You can either:
   - Check the flag's enabled state and read a configuration variable (`sort_method`) to determine which experience the user gets.
   - Check the flag variation directly and run the corresponding control or treatment code.
3. Track a conversion event called `purchased` to measure the experiment's impact. The `TrackEvent` method ties the purchase back to the A/B test and sends it to Optimizely so it displays on your [Experiment Results page](docId:_K6n7h_MZ8b0xn6yWPrrq).

```csharp
//Import Optimizely SDK
using OptimizelySDK;
using OptimizelySDK.Entity;

// Instantiate an Optimizely client
var optimizely = OptimizelyFactory.NewDefaultInstance("YOUR_SDK_KEY");

// Set custom user attributes
var attributes = new UserAttributes
{
    { "logged_in", true }
};

// Create a user context
var user = optimizely.CreateUserContext("user123", attributes);

var decision = user.Decide("product_sort");

// Execute code based on decision's variation key
if (string.IsNullOrEmpty(decision.VariationKey)) {
    Console.WriteLine("decision error: " + string.Join(" ", decision.Reasons));
} else if (decision.VariationKey == "control") {
    Console.WriteLine("control variation");
} else if (decision.VariationKey == "treatment") {
    Console.WriteLine("treatment variation");
} else {
    // Unknown variation
}

// Execute code based on flag enabled state
if (decision.Enabled) {
    var sortMethod = decision.Variables.ToDictionary()["sort_method"];
    Console.WriteLine($"sort_method: {sortMethod}");
}

// Track an event
user.TrackEvent("purchased");
```