Unleash

Dosaic.Plugins.Management.Unleash is a Dosaic plugin that integrates Unleash feature flag management into ASP.NET Core applications. It bridges the Unleash client SDK with the Microsoft.FeatureManagement abstraction, enabling gradual rollouts, experimentation, and kill-switch controls without redeployment.

Installation

dotnet add package Dosaic.Plugins.Management.Unleash

Or as a <PackageReference> in your .csproj:

<PackageReference Include="Dosaic.Plugins.Management.Unleash" Version="" />

Dependencies:

• Microsoft.FeatureManagement.AspNetCore — feature flag abstraction

• Unleash.Client — Unleash .NET client SDK

• AspNetCore.HealthChecks.Uris — URL-based health check

Configuration

The plugin reads its settings from the unleash section of your application configuration, bound via [Configuration("unleash")].

unleash:
  appName: "my-app"
  apiUri: "http://localhost:4242/api/"
  apiToken: "default:development.your-api-token-here"
  instanceTag: "instance-1"

Property	Description
appName	Name of your application, reported to the Unleash server
apiUri	Full URI to your Unleash API, e.g. http://localhost:4242/api/
apiToken	API token created in the Unleash web UI
instanceTag	Unique tag to identify this running instance

Usage

Checking a feature flag in code

Inject IFeatureManager and call IsEnabledAsync with the toggle name as defined in Unleash:

using Microsoft.FeatureManagement;

public class OrderService(IFeatureManager featureManager)
{
    public async Task<IActionResult> PlaceOrder(OrderRequest request)
    {
        if (await featureManager.IsEnabledAsync("new-checkout-flow"))
        {
            return await HandleNewCheckout(request);
        }

        return await HandleLegacyCheckout(request);
    }
}

Guarding a controller or action with [FeatureGate]

Apply [FeatureGate] at the controller or action level. When the toggle is disabled, the plugin returns a 404 Not Found response (via FeatureNotEnabledDisabledHandler).

using Microsoft.FeatureManagement.Mvc;

[ApiController, Route("beta")]
[FeatureGate("beta-api")]
public class BetaController : ControllerBase
{
    [HttpGet("feature-a")]
    [FeatureGate("feature-a")]
    public IActionResult GetFeatureA() => Ok("Feature A is active");

    [HttpPost("feature-b")]
    [FeatureGate("feature-b")]
    public IActionResult PostFeatureB() => Ok("Feature B is active");
}

MVC Razor views

Add the tag helper and use the <feature> tag to conditionally render view content:

@addTagHelper *, Microsoft.FeatureManagement.AspNetCore

<feature name="dark-mode">
    <link rel="stylesheet" href="~/css/dark.css" />
</feature>

<feature name="dark-mode" negate="true">
    <link rel="stylesheet" href="~/css/light.css" />
</feature>

Conditional middleware

Gate an entire middleware on a feature toggle:

app.UseMiddlewareForFeature<AnalyticsMiddleware>("analytics-tracking");

Conditional MVC filters

Register an MVC action filter that is only active when a toggle is enabled:

services.AddMvc(options =>
{
    options.Filters.AddForFeature<AuditFilter>("audit-logging");
});

Toggle types

FeatureToggleType provides constants for the standard Unleash toggle strategies:

using Dosaic.Plugins.Management.Unleash;

// Reference toggle types by their string constant
if (toggle.Type == FeatureToggleType.KillSwitch)
{
    // handle kill-switch logic
}

Constant	Value
FeatureToggleType.Release	"release"
FeatureToggleType.Experiment	"experiment"
FeatureToggleType.Operational	"operational"
FeatureToggleType.KillSwitch	"killSwitch"
FeatureToggleType.Permission	"permission"

Features

• Automatic Unleash context propagation — UnleashMiddlware ([Middleware(50)]) builds an UnleashContext per request, populating UserId (from HttpContext.User.Identity.Name), AppName, CurrentTime, RemoteAddress, and (optionally) SessionId when session middleware is registered.

• Microsoft.FeatureManagement integration — UnleashFeatureDefinitionProvider exposes all Unleash toggles as FeatureDefinition instances, and UnleashFilter ([FilterAlias("Unleash")]) evaluates them via the Unleash client, making IFeatureManager the single API for all feature checks.

• Disabled feature handler — when a [FeatureGate]-protected endpoint is accessed but the flag is off, FeatureNotEnabledDisabledHandler raises a NotFoundDosaicException, resulting in a 404 response.

• Health check — registers a readiness URL health check against {apiUri}/health under the name unleash.

• OpenTelemetry metrics — emits four counters automatically:

  Metric	Description
  dosaic_unleash_plugin_impressions_total	Number of impression events (labelled by featureName, enabled)
  dosaic_unleash_plugin_errors_total	Number of Unleash client error events
  dosaic_unleash_plugin_toggleUpdates_total	Number of toggle cache refresh events
  dosaic_unleash_plugin_unleash_filter_calls_total	Number of UnleashFilter evaluations (labelled by featureName, isEnabled)

• Structured logging — impression events are logged at Debug, toggle updates at Information, and errors at Error level.