dependency-injection .NET - Pure DI examples ASP.NET Core

Example

in Startup.cs

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddMvc();
    
    var controllerActivator = new CompositionRoot();
    services.AddSingleton<IControllerActivator>(controllerActivator);
}

CompositionRoot.cs

public class CompositionRoot : IControllerActivator, IDisposable
    {
        // Singletons
        private readonly ISingleton _singleton;

        public CompositionRoot()
        {
            // Create singletons
            _singleton = new Singleton();
        }

        public object Create(ControllerContext c) => this.Create(c.ActionDescriptor.ControllerTypeInfo.AsType());
        public void Release(ControllerContext c, object controller) => (controller as IDisposable)?.Dispose();

        public Controller Create(Type type)
        {
            // scoped 
            var scoped = new Scoped();
            // transient get new()-ed up below
            if (type == typeof(HomeController))
                return new HomeController(_singleton, scoped, new Transient());
            
            throw new InvalidOperationException($"Unknown controller {type}.");
        }

        public void Dispose()
        {
            // dispose stuff
        }
    }