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.NET Core Feature Flags

Introduction

Feature flags, also known as feature toggles or feature switches, are a useful software development approach for enabling or disabling individual features or code paths in an application without requiring a full deployment. They allow for the flexible management of feature releases, A/B testing, and control of feature visibility for different users or environments. In this post, we will look at how to implement feature flags in the .NET Core and give some examples of how to use them.

Why Are Feature Flags Used?

In software development, feature flags provide various benefits.

  • Developers: can deliver features to a subset of consumers incrementally, lowering the risk associated with big-bang deployments.
  • A/B Testing: Enabling a feature for a subset of users allows you to collect data on its performance and user engagement, allowing you to make data-driven decisions.
  • Emergency Rollbacks: If a new feature causes unanticipated problems, you can easily disable it without deploying a hotfix.
  • Environment-Specific Configuration: You can specify feature flags differently in different contexts (for example, development, staging, and production) without changing the code.
  • Toggles for Release: Features can be completed but buried behind a feature flag until they are ready for public release, preventing unfinished work from being disclosed inadvertently.

Implementing Feature Flags in .NET Core

Feature flags can be implemented in a variety of ways in.NET Core. In this section, we'll look at two common approaches: configuration and feature flag libraries.

1. Using Configuration

The use of configuration settings is a simple technique to provide feature flags. You can dynamically toggle feature flag values by storing them in your application's configuration, such as appsettings.json. Let's look at an example of this method.

Step 1. Define Feature Flags in Configuration.

// appsettings.json
{
  "FeatureFlags": {
    "NewFeatureEnabled": true,
    "BetaFeatureEnabled": false
  }
}

Step 2.  Access Feature Flags in the Code.

using Microsoft.Extensions.Configuration;

// ...

public class FeatureFlagService
{
    private readonly IConfiguration _configuration;

    public FeatureFlagService(IConfiguration configuration)
    {
        _configuration = configuration;
    }

    public bool IsNewFeatureEnabled()
    {
        return _configuration.GetValue<bool>("FeatureFlags:NewFeatureEnabled");
    }

    public bool IsBetaFeatureEnabled()
    {
        return _configuration.GetValue<bool>("FeatureFlags:BetaFeatureEnabled");
    }
}

Step 3. Use Feature Flags in our  Code.

public class MyService
{
    private readonly FeatureFlagService _featureFlagService;

    public MyService(FeatureFlagService featureFlagService)
    {
        _featureFlagService = featureFlagService;
    }

    public void DoSomething()
    {
        if (_featureFlagService.IsNewFeatureEnabled())
        {
            // New feature logic
        }
        else
        {
            // Old feature logic
        }
    }
}

This solution allows you to quickly control feature flags via configuration updates without modifying our code.

2. Using Feature Flag Libraries

Another alternative is to employ feature flag libraries, which provide more complex functionality and integrations. FeatureToggle, a prominent tool in the.NET ecosystem, provides a sophisticated framework for handling feature flags.

Step 1. Install the FeatureToggle NuGet Package first.

The following command will install the FeatureToggle NuGet package into your.NET Core project.

dotnet add package FeatureToggle

Step 2. Create Feature Toggles.

using FeatureToggle.Toggles;

public class NewFeatureToggle : SimpleFeatureToggle { }

public class BetaFeatureToggle : SimpleFeatureToggle { }

Step 3. Use Feature Toggles in our code.

public class MyService
{
    private readonly IFeatureToggle _newFeatureToggle;
    private readonly IFeatureToggle _betaFeatureToggle;

    public MyService(IFeatureToggle newFeatureToggle, IFeatureToggle betaFeatureToggle)
    {
        _newFeatureToggle = newFeatureToggle;
        _betaFeatureToggle = betaFeatureToggle;
    }

    public void DoSomething()
    {
        if (_newFeatureToggle.FeatureEnabled)
        {
            // New feature logic
        }
        else
        {
            // Old feature logic
        }

        if (_betaFeatureToggle.FeatureEnabled)
        {
            // Beta feature logic
        }
    }
}

In this approach, FeatureToggle provides a clean and structured way to manage feature flags in your application.

Conclusion

Feature flags are an important tool in modern software development because they allow developers to easily release, test, and control features. In.NET Core, feature flags can be implemented by settings or by utilizing libraries such as FeatureToggle for more complex capabilities. Regardless of the approach you use, feature flags can help you streamline the deployment process, collect useful user data, and guarantee that your application remains flexible and responsive to changing requirements.


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