Feature flag

feature.cs

using System;
using System.Collections.Concurrent;

namespace FeatureFlagTest
{
    class Program
    {
        static void Main(string[] args)
        {
            var home = new HomeController(FeatureFactory.Feature);

            home.Index();

            var evnt = new EventSample(FeatureFactory.Feature);

            evnt.Do();
        }
    }

    public interface IFeature
    {
        bool IsOn(string feature);
    }

    public sealed class Feature : IFeature
    {
        private readonly FeatureSettings _featureSettings;

        public Feature(FeatureSettings featureSettings) => _featureSettings = featureSettings;

        public bool IsOn(string feature)
        {
            if (string.IsNullOrEmpty(feature) || !_featureSettings.ContainsKey(feature)) return false;

            return _featureSettings[feature];
        }
    }

    public sealed class FeatureSettings : ConcurrentDictionary<string, bool>
    {
        public FeatureSettings() : base(StringComparer.OrdinalIgnoreCase) { }
    }

    public sealed class FeatureFactory
    {
        private static readonly Lazy<IFeature> _lazy = new Lazy<IFeature>(() => new Feature(GetFeatureSettings()));

        private static FeatureSettings GetFeatureSettings() => new FeatureSettings
        {
            ["welcome"] = true,
            ["events"] = false
        };

        public static IFeature Feature => _lazy.Value;

        private FeatureFactory() { }
    }

    public sealed class HomeController
    {
        private readonly IFeature _feature;

        public HomeController(IFeature feature) => _feature = feature;

        public void Index()
        {
            if (_feature.IsOn("welcome"))
            {
                //do something
            }
        }
    }

    public sealed class EventSample
    {
        private readonly IFeature _feature;

        public EventSample(IFeature feature) => _feature = feature;

        public void Do()
        {
            if (_feature.IsOn("ddd"))
            {
                //do something
            }
        }
    }
}