ASP.Net Core Feature Flags - Intro
Tags: aspnetcore, feature, featureflags, testing
Published: 2023-01-20 17:23:48

[ASP.Net](http://ASP.Net) Core is a free, open-source framework for building web applications and APIs. One of its powerful features is the ability to use feature flags, which allow developers to enable or disable certain functionality in their application without having to deploy new code.

## What is a Feature Flag?

A feature flag, also known as a feature toggle or a feature switch, is a simple mechanism that allows developers to control the behavior of their applications at runtime. By using feature flags, developers can easily test new functionality in a production environment without affecting the entire application. This can be especially useful for testing new features with a small subset of users before rolling them out to the entire user base.

## Implementing Feature Flags in [ASP.Net](http://ASP.Net) Core

Implementing feature flags in an [ASP.Net](http://ASP.Net) Core application is easy. You can use the Microsoft.FeatureManagement package, which is available on NuGet, to add feature flags to your application. This package provides a simple API that allows you to configure and manage feature flags in your application.

Here is an example of how to use feature flags in an [ASP.Net](http://ASP.Net) Core application:

1. Install the Microsoft.FeatureManagement package by running the following command in the package manager console:
    

```plaintext
Install-Package Microsoft.FeatureManagement
```

1. In the `Startup.cs` file, add the following line to the `ConfigureServices` method to enable feature management:
    

```csharp
services.AddFeatureManagement();
```

1. Create a new class to represent your feature flag. For example, if you are creating a feature flag for a new feature called "NewFeature", you would create a class like this:
    

```csharp
public class NewFeature : IFeature
{
}
```

1. In the `Startup.cs` file, add the following line to the `Configure` method to enable the feature flag:
    

```csharp
app.UseFeatureManagement();
```

1. In your controller or service, you can now use the `[FeatureGate]` attribute to enable or disable the feature based on the flag. For example, if you want to enable the "NewFeature" feature flag for a specific action in your controller, you would add the following attribute:
    

```csharp
[FeatureGate(NewFeature)]
public IActionResult MyAction()
{
// Code for the action goes here
}
```

This is just a basic example of how to use feature flags in an [ASP.Net](http://ASP.Net) Core application. With the Microsoft.FeatureManagement package, you can also configure feature flags using JSON files, environment variables, or a custom provider. You can also use the package to implement advanced features such as time-based rollouts and user-based targeting.

## Conclusion

Feature flags are a powerful tool that can help you improve the development and deployment process of your [ASP.Net](http://ASP.Net) Core application. By using feature flags, you can easily test new functionality in a production environment without affecting the entire application. This can save you time and resources and help you deliver new features to your users faster.