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Share Microsoft.Extensions.DependencyInjection.ServiceProvider configuration between projects

I have a solution that has the following projects
Acme.Core
Acme.Domain
Acme.Repositories
Acme.Services
Acme.Web
In the past I've used Unity for DI in full framework projects. I was able to register concrete objects to interface mappings in executable projects (web apps, console app, test apps).
I'm trying to implement the same approach with .NET Core. I wanted to first try using the Microsoft.Extensions.DependencyInjection library. Within the ASP.NET Core application it works great. Unfortunately I've run into an issue when I try to share/reference that instance with the registions to other projects, such as a .NET Standard library.
My idea was to inject the ServiceProvider into the constructor of the service:
public class AddressService : BaseService, IAddressService
{
private readonly IServiceProvider _serviceProvider;
public AddressService(IServiceProvider serviceProvider, string userOrProcessName)
{
_serviceProvider = serviceProvider;
}
public IReadOnlyList<IState> GetAllStates()
{
_serviceProvider.GetService<IAddressRepository>();
// other logic removed
}
}
I tried the following inside the Startup.ConfigureServices():
services.AddTransient<IAddressService>(s => new AddressService(HttpContext.RequestServices, Environment.UserName));
The issue I ran into is that I cannot reference HttpContext.RequestServices outside of a Controller. I haven't been able to figure another way of passing the ServiceProvider instance.
My questions:
How do pass a reference for the current ServiceProvider?
Is there a better design to accomplish my goal sharing the configuration of Microsoft.Extensions.DependencyInjection in multiple libraries?

Prevent injecting IServiceProvider into your application components; that leads to the Service Locator anti-pattern.
Instead, you should build up application components solely using Constructor Injection. This means that your AddressService should require IAddressRepository as constructor argument, not IServiceProvider. For instance:
public class AddressService : IAddressService
{
private readonly IAddressRepository repo;
public AddressService(IAddressRepository repo, IUserContext userContext)
{
this.repo = repo;
}
public IReadOnlyList<IState> GetAllStates()
{
// other logic removed
}
}
Also try to prevent injecting primites into your constructors. It's not a bad practice per se, but it does complicate object graph construction. Instead, either wrap the value into a class, in case its a configuration value, or hide it behind an abstraction (as shown above) in case it's a runtime value.
Both practices simplify both your application code and the Composition Root.
For instance, this will be the result of the previous AddressService redesign:
services.AddTransient<IAddressRepository, SqlAddressRepository>();
services.AddTransient<IAddressService, AddressService>();
services.AddScoped<IUserContext, UserContext>();
services.AddHttpContextAccessor();
Here, UserContext could be defined as follows:
public class UserContext : IUserContext
{
private readonly IHttpContextAccessor accessor;
public UserContext(IHttpContextAccessor accessor) => this.accessor = accessor;
public string UserName => this.accessor.HttpContext.User.Identity.Name;
}

In order to share configuration across multiple projects, you can put the configuration into a shared assembly, and register (not resolve) them in there. Many dependency injection libraries offer that functionality. e.g.
in Autofac you create a module (https://autofaccn.readthedocs.io/en/latest/configuration/modules.html) that takes a container builder to configure:
protected override void Load(ContainerBuilder builder) { ... }
SimpleInjector provides packages: https://simpleinjector.readthedocs.io/en/latest/howto.html#package-registrations
Unity can support something similar: Can I register my types in modules in Unity like I can in Autofac?
Ninject has a similar module feature: What is the intention of Ninject modules?
A similar feature has be created for Microsoft.Extensions.DependencyInjection: https://github.com/aruss/DotNetCore_ModularApplication
At a high level, you create a method that receives the DI container and adds your registrations to that container. If your DI framework doesn't provide hooks you need to manually call the method yourself, but the general concept doesn't change.
Splitting registrations into modules allows you to easily group similar sets of functionality while maintaining the flexibility of incorporating different sets of functionality into different projects. You could of course create a single shared assembly that registered the union of all dependencies for all projects, but that would carry around unnecessary baggage and result in a less reusable implementation.
The key point as Steven points out is that you configure the container and let it inject the dependencies rather than looking from the inside out for the dependencies.

Using NinjectModules from Service layer

I fail to understand how to probably setup my Ninject IoC container.
I have a Service layer which contains implementations of several services and implementation of my DbContext and ASP.NET Identity like so:
public class IdentityModule : NinjectModule
{
public override void Load()
{
Bind<IUserStore<User, int>>().To<UserService>().InSingletonScope();
Bind<UserManager<User, int>>().ToSelf().InSingletonScope();
Bind<IRoleStore<UserRole, int>>().To<UserRoleService>().InSingletonScope();
Bind<RoleManager<UserRole, int>>().ToSelf().InSingletonScope();
}
}
public class EntityFrameworkModule : NinjectModule
{
public override void Load()
{
Bind<EntityDbContext>().ToSelf();
Bind<ICreateDbModel>().To<DefaultDbModelCreator>();
Bind<IUnitOfWork>().To<EntityDbContext>();
Bind<IWriteEntities>().To<EntityDbContext>();
Bind<IReadEntities>().To<EntityDbContext>();
}
}
These are loaded into my NinjectWebCommen (MVC layer):
private static void RegisterServices(IKernel kernel)
{
var modules = new INinjectModule[]
{
new EntityFrameworkModule(),
new IdentityModule()
};
kernel.Load(modules);
}
Now my question is:
My EntityDbContext should be request scoped, but I am unable to set .InRequestScope() from my service layer. Should this INinjectModule then be moved to the MVC layer instead of lying in the service layer or should I reference Ninject.Web.Common in my service layer? This just seem to be a wrong way since the service layer is not a web-app.

This place where you wire everything together is called the
Composition Root in DI terminology
One of the suggestions is to create a bootstrap for all layers. Check this SO:
Where to locate Ninject modules in a multi-tier application

This is not the best answer but I have been having the same problem. First, make sure Ninject and Ninject.Web.Common are referenced in the service layer, and that you have a using statement for Ninject.Web.Common in your module class.
I couldn't find InRequestScope in Intellisense. I tried a few times opening and closing the project, and it finally showed up. Didn't do anything but close and re-open Visual Studio and it started working.

Resolving AutoFac dependencies inside Module class

I'm new to AutoFac and am currently using custom modules inside my app config to boot up some core F# systems. The code I'm using is
var builder = new ContainerBuilder();
builder.RegisterType<DefaultLogger>().As<IDefaultLogger>();
builder.RegisterModule(new ConfigurationSettingsReader("autofac"));
builder.Build();
And inside my app config I have the appropriate logic to start up the relevant systems. I would like to have access to the DefaultLogger inside my Modules. Metadata for the Module base class has the following options available to me:
protected virtual void AttachToComponentRegistration(IComponentRegistry componentRegistry, IComponentRegistration registration);
protected virtual void AttachToRegistrationSource(IComponentRegistry componentRegistry, IRegistrationSource registrationSource);
public void Configure(IComponentRegistry componentRegistry);
protected virtual void Load(ContainerBuilder builder);
I've only been using Load so far and I can't see any methods on the builder that would allow me to get at the logging service.

When registering something within your modules with autofac instead of using RegisterType method you might use Register method:
builder.Register(c =>
{
IComponentContext ctx = c.Resolve<IComponentContext();
IDefaultLogger logger = ctx.Resolve<IDefaultLogger>();
...do something with logger...
return ...return object you want to register...;
});

The answer turned out to be incredibly simple. I just added IComponentContext as a dependency to my Module's implementation
public class LocalActorSystemModule : Module {
private IComponentContext m_ComponentContext; // A service for resolving dependencies required by this module
public LocalActorSystemModule(IComponentContext componentContext) {
m_ComponentContext = componentContext;
}
And let AutoFac inject the IComponentContext for me. That way I can resolve any dependencies I require inside the module.

Rule of thumb for using every IoC/DI Container: Resolve once! => then you get all dependencies resolved for your requested object. If you try to resolve multiple times, register other objects (in the meantime) you're stuck in hell. Really. If you want to retrieve objects for different purposes at different places and time points (resolved from central registration) you may be looking for the Service Locator Pattern instead (but this is often described as an Anti-Pattern, too).
Modules have the purpose to bundle related registrations (conditionally) as statet in the Autofac documentation:
A module is a small class that can be used to bundle up a set of
related components behind a ‘facade’ to simplify configuration and
deployment.
... so if they are just a sum of registrations and the container has not yet been build you are not able to resolve and use an (even previously registered) component immediately (except calling a method on the registrant itself through OnActivate* hooks or when using instance registration, but I think this is not the case for your example). The components are just in the state of registration but the complete context is not ready for resolving. What would happen if you override the registration in another Module? Then you would have injected different objects... bad idea. Maybe you should rethink your application design and which objects have which responsibilities.
By the way: Logging is a cross cutting concern that is often "injected / resolved" by calling a separate static factory or service instead of doing constructor / property injection (see usage of Common.Logging for example).
public class MyModule : Module
{
private static readonly ILog Log = LogManager.GetLogger<MyModule>();
protected override void Load(ContainerBuilder builder)
{
Log.Debug(msg => msg("Hello")); // log whatever you want here
}
}
You can also try to use AOP libraries and weave the dependency into the Module (using reflection). But I don't think it's worth to try just for logging in a Module.
Anyway: #mr100 has already shown the right usage during registration. There you can also handle activation etc. but not do logging for the Module itself.

How can I access the Ninject kernel from a separate c# project?

I have a WCF application that uses Ninject (along with the NinjectWebCommon file) to take care of my dependency injection needs for the most part (this is done at app start); however, I have a separate project in the same solution that where I would like to use the kernel to resolve some dependencies at run-time. How can I get access to my kernel in this "other" project? Is it even possible?

How can I get access to my kernel in this "other" project?
You shouldn't do this. Only the startup path of your application should reference the container/kernel. This part is called the Composition Root. The kernel shouldn't be referenced outside the Composition Root; that would be an application of the Service Locator anti-pattern, and would cause all sorts of maintainability issues.
The 'trick' here is to define an abstract factory interface in your application. You can implement this factory inside your composition root. This will keep the kernel references only inside the composition root and will therefore not result in the Service Locator anti-pattern.
For instance:
// Defined in a core layer of the application
public interface IItemProcessorFactory {
IItemProcessor GetProcessor(ItemProcessorType type);
}
And inside your composition root (which could be a class or a namespace with multiple classes) you define an implementation:
// A nested type to exaggerate the fact that this is inside your Composition Root
private sealed class NinjectItemProcessorFactory : IItemProcessorFactory {
private readonly Kernel kernel;
public NinjectItemProcessorFactory(Kernel kernel) {
this.kernel = kernel;
}
public IItemProcessor GetProcessor(ItemProcessorType type) {
this.kernel.Get<IItemProcessor>(type.ToString());
}
}
And the factory can be registered as follows:
kernel.Bind<IItemProcessorFactory>().To<NinjectItemProcessorFactory>();

how to implement IOC without a global static service (non-service locator solution)?

we want to use Unity for IOC.
All i've seen is the implementation that there is one global static service (let's call it the the IOCService) which holds a reference to the Unity container, which registers all interface/class combinations and every class asks that object: give me an implementation for Ithis or IThat.
Frequently i see a response that this pattern is not good because it leads to a dependency from ALL classes to the IOCService (not to the Unity container because it is only known inside the IOCService).
But what i don't see often, is: what is the alternative way?
Michel
EDIT: found out that the global static service is called the service locator, added that to the title.

The alternative is to have a single instance of your container at the highest application level only, then use that container to resolve every object instance you need to create in that layer.
For example, the main method of most executables just looks like this (minus exception handling):
private static void main(string[] args) {
Container container = new Container();
// Configure the container - by hand or via file
IProgramLogic logic = container.Resolve<IProgramLogic>();
logic.Run();
}
Your program (represented here by the IProgramLogic instance) doesn't have to know anything about your container, because container.Resolve will create all its dependencies - and its dependencies' dependencies, on down to leaf classes with no dependencies of their own.
ASP.NET is a harder case, because web forms doesn't support constructor injection. I typically use Model-View-Presenter in my web forms applications, so my Page classes really only have one dependency each - on their presenter. I don't unit test them (everything interesting and testable is in my presenters, which I do test), and I don't ever substitute presenters. So I don't fight the framework - I just expose a container property on my HttpApplication class (in global.asax.cs) and use it directly from my Page files:
protected void Page_Load(object sender, EventArgs args) {
ICustomerPresenter presenter = Global.Container.Resolve<ICustomerPresenter>();
presenter.Load();
}
That's service locator of course - though the Page classes are the only thing coupled to the locator: your presenter and all of its dependencies are still fully decoupled from your IoC container implementation.
If you have a lot of dependencies in your Page files (that is, if you do not use Model-View-Presenter), or if it's important to you to decouple your Page classes from your Global application class, you should try to find a framework that integrates into the web forms request pipeline and use property injection (as suggested by Nicholas in the comments below) - or write your own IHttpModule and perform the property injection yourself.

+1 for knowing that Service Locator is a Bad Thing.
Problem is - Unity is not very sophisticated so I don't know how easy/hard is it to do IoC the right way with it.
I wrote few blogposts recently that you might find useful.
How I use IoC Containers
Pulling from the container

Instead of using the container explicitly, use it implicitly by leveraging constructor / property injection instead. Create a core class (or set of core classes) that depend on all the major pieces of your application.
Most containers will let you put ISomething[] in your constructor and it will inject all instances of ISomething into your class.
This way, when you bootstrap your application:
Instantiate your container
Register all your goodies
Resolve the core classes (this will pull in all the other dependencies you need)
Run the "main" part of the application
Now, depending on the type of application you are writing, there are different strategies for avoiding marking the IoC container as "static".
For ASP.NET web applications, you'll probably end up storing the container in the Application State. For ASP.NET MVC applications, you need to change out the Controller Factory.
For desktop applications, things get more complicated. Caliburn uses an interesting solution to this problem using the IResult construct (this is for WPF applications but could be adapted for Windows Forms as well.

In theory, to not have to worry about having a static IoC instance, you need to follow the Fight Club Rule - i.e. not to talk about the fight club - i.e. not to mention the IoC container.
This means that your components should largely be unaware about the IoC container. It should only be used at the topmost level when registering components. If a class needs to resolve something, it should really be injected as a dependency.
The trivial case is easy enough. If PaymentService depends on IAccount, the latter should be injected by IoC:
interface IAccount {
Deposit(int amount);
}
interface CreditCardAccount : IAccount {
void Deposit(int amount) {/*implementation*/}
int CheckBalance() {/*implementation*/}
}
class PaymentService {
IAccount account;
public PaymentService (IAccount account) {
this.account = account;
}
public void ProcessPayment() {
account.Deposit(5);
}
}
//Registration looks something like this
container.RegisterType<IAccount, CreditCardAccount>();
container.RegisterType<PaymentService>();
The not so trivial case is where you want to inject multiple registrations. This especialy applies when you are doing any sort of Converntion Over Configuration and creating an object from a name.
For our payment example, say you want to enumerate through all accounts and check their balances:
class PaymentService {
IEnumerable<IAccount> accounts;
public PaymentService (IEnumerable<IAccount> accounts) {
this.accounts = accounts;
}
public void ProcessPayment() {
foreach(var account in accounts) {
account.Chackbalance();
}
}
}
Unity has the ability to register multiple interface to class mappings (they have to have different names thought). It does not, however, automatically inject those into classes that take collections of those registered interfaces. So, the above example will throw a resolution failed exception at runtime.
If you don't care that those objects live forever, you can register PaymentService in a more static fashion:
container.RegisterType<PaymentService>(new InjectionConstructor(container.ResolveAll<IAccount>()));
The above code will register PaymentService and will use a collection of IAccount instances that is resolved at registration time.
Alternatively, you can pass an instance of the container itself as a dependency and let PaymentService perform resolution of accounts. This is not quite following the Fight Club Rule, but is slightly less smelly than static Service Locator.
class PaymentService {
IEnumerable<IAccount> accounts;
public PaymentService (IUnityContainer container) {
this.accounts = container.ResolveAll<IAccount>();
}
public void ProcessPayment() {
foreach(var account in accounts) {
account.Chackbalance();
}
}
}
//Registration is pretty clean in this case
container.RegisterType<IAccount, CreditCardAccount>();
container.RegisterType<PaymentService>();
container.RegisterInstance<IUnityContainer>(container);

If your concern is having a dependency on Unity throughout your application, you can combine the service locator with a facade to hide the IOC implementation. In this way, you do not create a dependency on Unity in your application, only on having something that can resolve types for you.
For example:
public interface IContainer
{
void Register<TAbstraction,TImplementation>();
void RegisterThis<T>(T instance);
T Get<T>();
}
public static class Container
{
static readonly IContainer container;
public static InitializeWith(IContainer containerImplementation)
{
container = containerImplementation;
}
public static void Register<TAbstraction, TImplementation>()
{
container.Register<TAbstraction, TImplementation>();
}
public static void RegisterThis<T>(T instance)
{
container.RegisterThis<T>(instance);
}
public static T Get<T>()
{
return container.Get<T>();
}
}
Now all you need is an IContainer implementation for your IOC container of choice.
public class UnityContainerImplementation : IContainer
{
IUnityContainer container;
public UnityContainerImplementation(IUnityContainer container)
{
this.container = container;
}
public void Register<TAbstraction, TImplementation>()
{
container.Register<TAbstraction, TImplementation>();
}
public void RegisterThis<T>(T instance)
{
container.RegisterInstance<T>(instance);
}
public T Get<T>()
{
return container.Resolve<T>();
}
}
Now you have a service locator that is a facade for IOC services, and can configure your service locator to use Unity or any other IOC container. The rest of the application has no dependency on the IOC implementation.
To configure your service locator:
IUnityContainer unityContainer = new UnityContainer();
UnityContainerImplementation containerImpl = new UnityContainerImplementation(unityContainer);
Container.InitializeWith(containerImpl);
For testing, you can create a stub of IContainer that returns whatever you want, and initialize Container with that.