.NET SDK - Feature management

Package: WestyxNexus.FeatureManagement (v0.11.0+) Serves Nexus feature flags to Microsoft.FeatureManagement, so IFeatureManager and the [FeatureGate] attribute work against flags managed in the Nexus console.

dotnet add package WestyxNexus.FeatureManagement

builder.Services.AddWestyxNexus(o =>
{
    o.BaseUrl = builder.Configuration["Nexus:BaseUrl"]!;
    o.ApiKey  = builder.Configuration["Nexus:ApiKey"];
});
builder.Services.AddWestyxNexusFeatureManagement();

public sealed class CheckoutController(IFeatureManager features)
{
    public async Task<IActionResult> Index()
    {
        if (await features.IsEnabledAsync("new.checkout"))
            return View("NewCheckout");

        return View("Checkout");
    }
}

Or declaratively:

[FeatureGate("new.checkout")]
public IActionResult NewCheckout() => View();

No network call per evaluation

Every read comes from the SDK’s in-memory cache. IsEnabledAsync does not make an HTTP request - it looks up a dictionary. The cache is kept current by the SDK’s own TTL polling and SSE stream, so a flag flipped in the Nexus console takes effect without a restart and without any FeatureManagement-side reconfiguration.

How a Nexus flag maps

Nexus flag	`FeatureDefinition`
`is_active: true`	`EnabledFor` = a single `AlwaysOn` filter
`is_active: false`	`EnabledFor` empty
not defined	`null` - the feature is undefined, not disabled

This is exactly how Microsoft’s own configuration provider represents "MyFeature": true and false, so Nexus flags behave identically to configuration-defined ones. is_active is computed server-side from is_enabled plus the flag’s schedule window, so a scheduled flag turns itself on and off with no client involvement.

Scope: boolean state only

A Nexus flag also supports percentage rollout and cohort targeting, both evaluated server-side against a supplied user context. Those are not routed through IFeatureManager.

This is deliberate rather than unfinished. A targeting-aware flag exposed through a boolean-only bridge would silently evaluate as its untargeted default - a rollout you believe is at 10% would read as fully on or fully off, with nothing to indicate it. Being unsupported is safer than being quietly wrong.

For percentage rollout and targeting today, call the client directly:

var results = await nexus.EvaluateABAsync(
    new[] { "new.checkout" },
    userId: currentUser.Id,
    attributes: new Dictionary<string, object> { ["plan"] = "pro" });

Per-user targeting through the FeatureManagement and OpenFeature bridges is planned across all providers as one coordinated change.

Registration order

The provider is registered with TryAddSingleton before AddFeatureManagement() runs, so it wins over the configuration-backed provider that AddFeatureManagement() would otherwise install. If you need both sources, register your own composite IFeatureDefinitionProvider instead of calling AddWestyxNexusFeatureManagement().

Dependency injection
OpenFeature integration - the vendor-neutral alternative
Design decisions

Overview

Backend SDKs

Browser SDKs

OpenFeature Providers

.NET SDK - Feature management

No network call per evaluation

How a Nexus flag maps

Scope: boolean state only

Registration order

Next

​No network call per evaluation

​How a Nexus flag maps

​Scope: boolean state only

​Registration order

​Next

No network call per evaluation

How a Nexus flag maps

Scope: boolean state only

Registration order

Next