The Rollouts Developer Hub

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Quickstart guide for Optimizely Rollouts

Welcome to the quickstart guide for Optimizely's C# SDK. The instructions below will help you implement Optimizely Rollouts and launch your first feature flag.

This guide will help you:

  1. Install the SDK
  2. Instantiate the Optimizely Client
  3. Create a feature flag
  4. Roll out the feature

1. Install the SDK

The C# SDK is distributed through NuGet.

For Windows, to install, run the command Install-Package Optimizely.SDK in the Package Manager Console:

PM> Install-Package Optimizely.SDK

The package is on NuGet at The full source code is at

2. Configure Optimizely when your app starts

The datafile stores the configuration for all your features and rollouts. Whenever you make a change in Optimizely, the datafile is automatically updated so you can pull configuration changes down into your application.

The sample below shows how you can get a local copy of the datafile from our server and instantiate a client with it. Later, you'll want to adjust this code to handle datafile updates.

string datafile = string.Empty;
var url = "<Your_SDK_Key>.json";
using(var webClient = new System.Net.WebClient()){

  // To refresh on every request
  webClient.CachePolicy = new System.Net.Cache.RequestCachePolicy(System.Net.Cache.RequestCacheLevel.NoCacheNoStore);
  datafile = webClient.DownloadString(url);

var optimizelyClient = new OptimizelySDK.Optimizely(datafile);

If you see <Your_SDK_Key> in the sample above, here's where to find your SDK Key:

  1. Navigate to Settings > Environments.
  2. Copy the SDK Key / Primary URL.
Click to enlarge

Click to enlarge

3. Create a feature flag

Choose a feature in your app to turn on and off with a feature flag. For your first flag, consider starting with a link or visual element that's simple to change, show, or hide based on a Boolean.

To set up your first feature flag, navigate to Features > Create New Feature.

Here's how to set it up:

Click to enlarge.

Click to enlarge.

After saving, use the Boolean Is Feature Enabled function to show, hide, or change some visual part of your application. You should see a value of false from this function because you haven't rolled out the feature yet. You'll turn it on in the next step.

bool enabled = OptimizelyClient.IsFeatureEnabled("new_feature", "user123");

The userID enables you to create consistent experiences for a user across multiple visits, but you don't need it for this quickstart. Make the userID any non-null string for now.

4. Roll out the feature

Navigate back to Features and select your feature flag.

You'll return to this modal whenever you want to update this feature flag. For example, roll out your feature incrementally by moving the slider up by 10% per day or show it to a certain group of users. Move it to 100% for a big reveal, or 0% if issues arise in production. No code deployment necessary.

Click to enlarge.

Click to enlarge.

A basic way to confirm that your feature flag is working:

Show the feature to yourself

  1. Navigate to your feature.
  2. Toggle it ON and move the slider to 100% traffic. Click Save.
  3. Confirm that you see the feature.

Hide the feature from yourself

  1. Navigate back to the feature.
  2. Toggle it OFF. Click Save.
  3. Confirm that you no longer see the feature.

When you're ready, go ahead and launch your feature in production. Come back and adjust its configuration any time, without deploying code.

Updated 5 months ago


Quickstart guide for Optimizely Rollouts

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