Disclaimer: As of early 2015, there is a great comparison of IoC Container features from Jimmy Bogard, here is a summary:
Compared Containers:
- Autofac
- Ninject
- Simple Injector
- StructureMap
- Unity
- Windsor
The scenario is this: I have an interface, IMediator, in which I can send a single request/response or a notification to multiple recipients:
public interface IMediator
{
TResponse Send<TResponse>(IRequest<TResponse> request);
Task<TResponse> SendAsync<TResponse>(IAsyncRequest<TResponse> request);
void Publish<TNotification>(TNotification notification)
where TNotification : INotification;
Task PublishAsync<TNotification>(TNotification notification)
where TNotification : IAsyncNotification;
}
I then created a base set of requests/responses/notifications:
public class Ping : IRequest<Pong>
{
public string Message { get; set; }
}
public class Pong
{
public string Message { get; set; }
}
public class PingAsync : IAsyncRequest<Pong>
{
public string Message { get; set; }
}
public class Pinged : INotification { }
public class PingedAsync : IAsyncNotification { }
I was interested in looking at a few things with regards to container support for generics:
- Setup for open generics (registering IRequestHandler<,> easily)
- Setup for multiple registrations of open generics (two or more
INotificationHandlers)
Setup for generic variance (registering handlers for base INotification/creating request pipelines)
My handlers are pretty straightforward, they just output to console:
public class PingHandler : IRequestHandler<Ping, Pong> { /* Impl */ }
public class PingAsyncHandler : IAsyncRequestHandler<PingAsync, Pong> { /* Impl */ }
public class PingedHandler : INotificationHandler<Pinged> { /* Impl */ }
public class PingedAlsoHandler : INotificationHandler<Pinged> { /* Impl */ }
public class GenericHandler : INotificationHandler<INotification> { /* Impl */ }
public class PingedAsyncHandler : IAsyncNotificationHandler<PingedAsync> { /* Impl */ }
public class PingedAlsoAsyncHandler : IAsyncNotificationHandler<PingedAsync> { /* Impl */ }
Autofac
var builder = new ContainerBuilder();
builder.RegisterSource(new ContravariantRegistrationSource());
builder.RegisterAssemblyTypes(typeof (IMediator).Assembly).AsImplementedInterfaces();
builder.RegisterAssemblyTypes(typeof (Ping).Assembly).AsImplementedInterfaces();
- Open generics: yes, implicitly
- Multiple open generics: yes, implicitly
- Generic contravariance: yes, explicitly
Ninject
var kernel = new StandardKernel();
kernel.Components.Add<IBindingResolver, ContravariantBindingResolver>();
kernel.Bind(scan => scan.FromAssemblyContaining<IMediator>()
.SelectAllClasses()
.BindDefaultInterface());
kernel.Bind(scan => scan.FromAssemblyContaining<Ping>()
.SelectAllClasses()
.BindAllInterfaces());
kernel.Bind<TextWriter>().ToConstant(Console.Out);
- Open generics: yes, implicitly
- Multiple open generics: yes, implicitly
- Generic contravariance: yes, with user-built extensions
Simple Injector
var container = new Container();
var assemblies = GetAssemblies().ToArray();
container.Register<IMediator, Mediator>();
container.Register(typeof(IRequestHandler<,>), assemblies);
container.Register(typeof(IAsyncRequestHandler<,>), assemblies);
container.RegisterCollection(typeof(INotificationHandler<>), assemblies);
container.RegisterCollection(typeof(IAsyncNotificationHandler<>), assemblies);
- Open generics: yes, explicitly
- Multiple open generics: yes, explicitly
- Generic contravariance: yes, implicitly (with update 3.0)
StructureMap
var container = new Container(cfg =>
{
cfg.Scan(scanner =>
{
scanner.AssemblyContainingType<Ping>();
scanner.AssemblyContainingType<IMediator>();
scanner.WithDefaultConventions();
scanner.AddAllTypesOf(typeof(IRequestHandler<,>));
scanner.AddAllTypesOf(typeof(IAsyncRequestHandler<,>));
scanner.AddAllTypesOf(typeof(INotificationHandler<>));
scanner.AddAllTypesOf(typeof(IAsyncNotificationHandler<>));
});
});
- Open generics: yes, explicitly
- Multiple open generics: yes, explicitly
- Generic contravariance: yes, implicitly
Unity
container.RegisterTypes(AllClasses.FromAssemblies(typeof(Ping).Assembly),
WithMappings.FromAllInterfaces,
GetName,
GetLifetimeManager);
/* later down */
static bool IsNotificationHandler(Type type)
{
return type.GetInterfaces().Any(x => x.IsGenericType && (x.GetGenericTypeDefinition() == typeof(INotificationHandler<>) || x.GetGenericTypeDefinition() == typeof(IAsyncNotificationHandler<>)));
}
static LifetimeManager GetLifetimeManager(Type type)
{
return IsNotificationHandler(type) ? new ContainerControlledLifetimeManager() : null;
}
static string GetName(Type type)
{
return IsNotificationHandler(type) ? string.Format("HandlerFor" + type.Name) : string.Empty;
}
- Open generics: yes, implicitly
- Multiple open generics: yes, with user-built extension
- Generic contravariance: derp
Windsor
var container = new WindsorContainer();
container.Register(Classes.FromAssemblyContaining<IMediator>().Pick().WithServiceAllInterfaces());
container.Register(Classes.FromAssemblyContaining<Ping>().Pick().WithServiceAllInterfaces());
container.Kernel.AddHandlersFilter(new ContravariantFilter());
- Open generics: yes, implicitly
- Multiple open generics: yes, implicitly
- Generic contravariance: yes, with user-built extension
