Develop Reference

Autofac method level interception with Castle DynamicProxy in .NET Core 2

I currently wrote an Interceptor which code is below
public class TransactionalInterceptor : IInterceptor
{
public void Intercept(IInvocation invocation)
{
using (var transaction = ...)
{
try
{
invocation.Proceed();
transaction.Commit();
}
catch
{
transaction.Rollback();
}
finally
{
transaction.Dispose();
}
}
}
}
but when register this interceptor it will apply to all methods. I have a service class with a repository injected having CRUD methods.
I don't want a transaction to be opened for query methods.
I read this link but I cannot figure out how to apply it to my code
http://docs.autofac.org/en/latest/advanced/adapters-decorators.html#decorators
I don't know who to refactor my TransactionalInterceptor (and register it) to use it in a class like this code
[Intercept(typeof(LoggerInterceptor))] //logger
public class SomeService : ISomeService
{
private readonly ISomeRepository someRepository;
public SomeService(SomeRepository someRepository)
{
this.someRepository = someRepository;
}
public IEnumerable<SomeDto> GetAll()
{
// code
}
public SomeDto GetById()
{
// code
}
[Transactional]
public int Create(SomeDto someDto)
{
// code to insert
}
}

The invocation parameter of the Intercept method contains a Method property which is a MethodInfo of the method currently intercepted.
You can use this property to do what you want.
For example by using the method name :
public void Intercept(IInvocation invocation)
{
if (invocation.MethodInvocationTarget.Name != nameof(ISomeService.Create))
{
invocation.Proceed();
return;
}
using (var transaction = ...)
{
try
{
invocation.Proceed();
transaction.Commit();
}
catch
{
transaction.Rollback();
}
finally
{
transaction.Dispose();
}
}
}
or based on an attribute from the target method :
if (!invocation.MethodInvocationTarget
.CustomAttributes
.Any(a => a.AttributeType == typeof(TransactionalAttribute)))
You can also use the IInterceptorSelector type but it requires more work to register it with Autofac

I solved the problem with ProxyGenerationHook. See the answer
Create your custom attribute for selecting which method to intercept. This attribute's target should be Method.
[System.AttributeUsage(AttributeTargets.Method, Inherited = true, AllowMultiple = true)]
sealed class UseInterceptorAttribute : Attribute
{
public UseInterceptorAttribute()
{
}
}
Create your service interface and service class:
public interface ISomeService
{
void GetWithoutInterceptor();
[UseInterceptor]
void GetWithInterceptor();
}
public class SomeService
{
void GetWithoutInterceptor()
{
//This method will not be intercepted...
}
[UseInterceptor]
void GetWithInterceptor()
{
//This method will be intercepted...
}
}
Create your ProxyGenerationHook
public class SomeServiceProxyGenerationHook : IProxyGenerationHook
{
public void MethodsInspected()
{
}
public void NonProxyableMemberNotification(Type type, MemberInfo memberInfo)
{
}
public bool ShouldInterceptMethod(Type type, MethodInfo methodInfo)
{
return methodInfo
.CustomAttributes
.Any(a => a.AttributeType == typeof(UseInterceptorAttribute));
}
}
Don't use attributes for enabling interceptors. Enable it when
registering your service like this:
public class AutofacDependencyResolver
{
private readonly IContainer _container;
public AutofacDependencyResolver()
{
_container = BuildContainer();
}
private IContainer BuildContainer()
{
var proxyGenerationOptions = new ProxyGenerationOptions(new ProductServiceProxyGenerationHook());
builder.RegisterType<SomeService>()
.As<ISomeService>()
.EnableInterfaceInterceptors(proxyGenerationOptions)
.InterceptedBy(typeof(TransactionalInterceptor))
builder.Register(c => new TransactionalInterceptor());
return builder.Build();
}
public T GetService<T>()
where T:class
{
var result = _container.TryResolve(out T serviceInstance);
return serviceInstance ?? throw new Exception($"The service could not found: {nameof(T)}");
}
}
This solution is following this article
Also I uploaded the minimal example about this solution.

also can try, it is simple https://fs7744.github.io/Norns.Urd/index.html
public class AddTenInterceptorAttribute : AbstractInterceptorAttribute
{
public override void Invoke(AspectContext context, AspectDelegate next)
{
next(context);
AddTen(context);
}
private static void AddTen(AspectContext context)
{
if (context.ReturnValue is int i)
{
context.ReturnValue = i + 10;
}
else if(context.ReturnValue is double d)
{
context.ReturnValue = d + 10.0;
}
}
public override async Task InvokeAsync(AspectContext context, AsyncAspectDelegate next)
{
await next(context);
AddTen(context);
}
}
[AddTenInterceptor]
public interface IGenericTest<T, R> : IDisposable
{
// or
//[AddTenInterceptor]
T GetT();
}

Invoking a different constructor with autofixture [duplicate]

I'm using AutoFixture and I'd like to use a specific constructor.
I have the following code and I like to select the constructor with ITemplateParameterHandler.
public sealed class TemplateSegmentHandler : ITemplateSegmentHandler
{
public TemplateSegmentHandler(ITemplateIterator iterator)
: this(new TemplateParameterHandler(iterator))
{
Contract.Requires(iterator != null);
}
public TemplateSegmentHandler(ITemplateParameterHandler parameterHandler)
{
Contract.Requires(parameterHandler != null);
_parameterHandler = parameterHandler;
_parameterHandler.Ending += EndingParameter;
}
// ...
}
EDIT:
I want to inject the following fake implementation. (I'm using NSubstitute to create the fake object.)
public sealed class CustomTemplateParameter : ICustomization
{
private readonly ITemplateParameterHandler _context;
public CustomTemplateParameter()
{
_context = Substitute.For<ITemplateParameterHandler>();
}
public void Customize(IFixture fixture)
{
fixture.Customize<ITemplateParameterHandler>(c => c.FromFactory(() => _context));
}
public CustomTemplateParameter SetCatchAll(bool isCatchAll)
{
_context.IsCatchAll.Returns(isCatchAll);
return this;
}
}
Here is the way I'm trying to use it.
[Fact]
public void Should_return_true_when_the_segment_has_a_catch_all_parameter()
{
TemplateSegmentHandler segmentHandler = new Fixture().Customize(new TemplateSegmentHandlerFixture())
.Customize(new CustomTemplateParameterHandler()
.SetCatchAll(true))
.Create<TemplateSegmentHandler>();
segmentHandler.Parameter.Start();
segmentHandler.Parameter.End();
segmentHandler.HasCatchAll.Should().BeTrue();
}
But it still selects the wrong constructor and I'm getting the following error.
Ploeh.AutoFixture.ObjectCreationExceptionAutoFixture was unable to create an instance from Somia.Web.Routing.Template.ITemplateIterator, most likely because it has no public constructor, is an abstract or non-public type.
Request path:
Somia.Web.Routing.Template.TemplateSegmentHandler -->
Somia.Web.Routing.Template.ITemplateIterator iterator -->
Somia.Web.Routing.Template.ITemplateIterator

I ended up implementing IMethodQuery and select the ctor I wanted.
public sealed class SelectedFirstConstructorQuery : IMethodQuery
{
private readonly Type _type;
public SelectedFirstConstructorQuery(Type type)
{
_type = type;
}
public IEnumerable<IMethod> SelectMethods(Type type)
{
if (type == null)
{
throw new ArgumentNullException("type");
}
return from ci in type.GetConstructors()
let parameter = ci.GetParameters().First()
where parameter.ParameterType == _type
select new ConstructorMethod(ci) as IMethod;
}
}
Usage:
fixture.Customize<TemplateSegmentHandler>(c => c.FromFactory(new MethodInvoker(new SelectedFirstConstructorQuery(typeof(ITemplateParameterHandler)))));

One possible way:
var parameterHandler = fixture.Create<ITemplateParameterHandler>();
var segmentHandler = fixture.Build<TemplateSegmentHandler>()
.FromFactory(() => new TemplateSegmentHandler(parameterHandler));
fixture.Inject(segmentHandler);

How to use the type being resolved to resolve a dependency

I have several classes that take a dependency of type ILogger. The implementation of ILogger needs to know the type for which it is the logger, i.e. the ILogger for Foo will be new Logger(typeof(Foo)), for Bar it will be new Logger(typeof(Bar)), etc.
I would like the proper logger to be injected automatically by Unity; in other words, when I call container.Resolve<Foo>(), I want a new Logger(typeof(Foo)) to be injected into the Foo instance.
How can I set this up in Unity? Is there a way to pass the type being resolved to the dependency?
(In my real code, I actually have a ILoggerFactory with a Create method, which also takes a type as a parameter. So I could just pass the factory to my classes, and they would call Create themselves to get the appropriate logger, but it's not as elegant as what I'd like to achieve)
Some code to make things clearer:
interface ILogger
{
...
}
class Logger : ILogger
{
private readonly Type _type;
public Logger(Type type)
{
_type = type;
}
...
}
class Foo
{
private readonly ILogger _logger;
public Foo(ILogger logger) // here I want a Logger with its type set to Foo
{
_logger = logger;
}
}
This related question shows exactly what I'm trying to do, and the accepted answer is exactly the kind of thing I'm looking for... but it's for NInject, not Unity.

Here's a container extension that will set the Type parameter of the Logger constructor to the Type that the ILogger is being injected into.
The transient IBuilderContext.Policies is used to store the type that the ILogger is being injected into.
Maybe it's more complicated than it needs to be but this seems to work
public class LoggerExtension : UnityContainerExtension
{
public static NamedTypeBuildKey LoggerBuildKey = new NamedTypeBuildKey<Logger>();
protected override void Initialize()
{
Context.Strategies.Add(new LoggerTrackingPolicy(), UnityBuildStage.TypeMapping);
Context.Strategies.Add(new LoggerBuildUpStrategy(), UnityBuildStage.PreCreation);
}
}
public class LoggerTrackingPolicy : BuilderStrategy
{
public LoggerTrackingPolicy()
{
}
public override void PreBuildUp(IBuilderContext context)
{
if (context.BuildKey.Type != typeof(Logger))
{
var loggerPolicy = context.Policies.Get<ILoggerPolicy>(LoggerExtension.LoggerBuildKey);
if (loggerPolicy == null)
{
loggerPolicy = new LoggerPolicy();
context.Policies.Set<ILoggerPolicy>(loggerPolicy, LoggerExtension.LoggerBuildKey);
}
loggerPolicy.Push(context.BuildKey.Type);
}
}
}
public class LoggerBuildUpStrategy : BuilderStrategy
{
public LoggerBuildUpStrategy()
{
}
public override void PreBuildUp(IBuilderContext context)
{
if (context.BuildKey.Type == typeof(Logger))
{
var policy = context.Policies.Get<ILoggerPolicy>(LoggerExtension.LoggerBuildKey);
Type type = policy.Peek();
if (type != null)
{
context.AddResolverOverrides(new ParameterOverride("type", new InjectionParameter(typeof(Type), type)));
}
}
}
public override void PostBuildUp(IBuilderContext context)
{
if (context.BuildKey.Type != typeof(Logger))
{
var policy = context.Policies.Get<ILoggerPolicy>(LoggerExtension.LoggerBuildKey);
policy.Pop();
}
}
}
public interface ILoggerPolicy : IBuilderPolicy
{
void Push(Type type);
Type Pop();
Type Peek();
}
public class LoggerPolicy : ILoggerPolicy
{
private Stack<Type> types = new Stack<Type>();
public void Push(Type type)
{
types.Push(type);
}
public Type Peek()
{
if (types.Count > 0)
{
return types.Peek();
}
return null;
}
public Type Pop()
{
if (types.Count > 0)
{
return types.Pop();
}
return null;
}
}
How it works is: when a type that is not a Logger is trying to be resolved then, during the TypeMapping stage (before any creation), the type is pushed on a stack. Later, before creation, if the type is a Logger then the type it is being injected into is peeked from the stack and that type used as a resolver override. After creation, if the type is not a Logger, it is popped from the stack.
And some code to make sure it's working (I added a Type property to the logger just to verify it's set properly):
class Program
{
static void Main(string[] args)
{
IUnityContainer container = new UnityContainer();
container.RegisterType<ILogger, Logger>();
container.AddNewExtension<LoggerExtension>();
var a = container.Resolve<A>();
var b = container.Resolve<B>();
var c = container.Resolve<C>();
var d = container.Resolve<D>();
var x = container.Resolve<X>();
}
}
public interface ILogger
{
Type Type { get; }
}
public class Logger : ILogger
{
private readonly Type _type;
public Logger(Type type)
{
_type = type;
}
public Type Type { get { return _type; } }
}
public class A
{
public A(ILogger logger)
{
System.Diagnostics.Debug.Assert(logger.Type == typeof(A));
}
}
public class B
{
public B(ILogger logger)
{
System.Diagnostics.Debug.Assert(logger.Type == typeof(B));
}
}
public class C
{
public C(A a, D d, B b, ILogger logger)
{
System.Diagnostics.Debug.Assert(logger.Type == typeof(C));
}
}
public class D
{
public D()
{
}
}
public class X
{
public X(Y y)
{
}
}
public class Y
{
public Y(ILogger logger)
{
System.Diagnostics.Debug.Assert(logger.Type == typeof(Y));
}
}

As #spotco suggested, I would also recommend generics. The unity registration would be done using "open generics" as shown here. This single registration gives you the ability to resolve any type in the generics parameter of Logger.
unityContainer.RegisterType(typeof(ILogger<>), typeof(Logger<>));
Using that registration, you can resolve the instance using constructor injection like this.
public class MyClass
{
public MyClass(ILogger<MyClass> logger) { ... }
}
More info here.

Registering different UnitOfWorks per each module for a generic CommandHandler using structuremap

I'm using CQRS pattern in my recent project, and used EF code first in my DAL, so I defined some generic CommandHandlers to do Insert/Update/Delete:
public class InsertCommandHandler<TEntity> : ICommandHandler<InsertCommandParameter<TEntity>>
where TEntity : BaseEntity, IAggregateRoot<TEntity>, new()
{
private readonly IUnitOfWork _uow;
public InsertCommandHandler(IUnitOfWork uow)
{
_uow = uow;
}
public void Handle(InsertCommandParameter<TEntity> parameter)
{
var entity = parameter.Entity;
_uow.Repository<TEntity>().Add(entity);
}
}
public interface ICommandParameter
{
}
public abstract class BaseEntityCommandParameter<T> : ICommandParameter
where T : BaseEntity, new()
{
public T Entity { get; set; }
protected BaseEntityCommandParameter()
{
Entity = new T();
}
}
public class InsertCommandParameter<T> : BaseEntityCommandParameter<T> where T : class, new()
{
}
As you see I injected the IUnitOfWork to the InsertCommandHandler constructor.
public interface IUnitOfWork : IDisposable
{
IRepository<T> Repository<T>() where T : BaseEntity, IAggregateRoot<T>,new ();
void Commit();
}
I used Structuremap 3 as my IoC Container, So I defined following conversion to resolve ICommandHandlers for each BaseEntity types(using custom registration conventions for partially closed types):
public class CRUDCommandRegistrationConvention : StructureMap.Graph.IRegistrationConvention
{
private static readonly
Type _openHandlerInterfaceType = typeof(ICommandHandler<>);
private static readonly
Type _openInsertCommandType = typeof(InsertCommandParameter<>);
private static readonly
Type _openInsertCommandHandlerType = typeof(InsertCommandHandler<>);
private static readonly
Type _openUpdateCommandType = typeof(UpdateCommandParameter<>);
private static readonly
Type _openUpdateCommandHandlerType = typeof(UpdateCommandHandler<>);
private static readonly
Type _openDeleteCommandType = typeof(DeleteCommandParameter<>);
private static readonly
Type _openDeleteCommandHandlerType = typeof(DeleteCommandHandler<>);
public void Process(Type type, Registry registry)
{
if (!type.IsAbstract && typeof(BaseEntity).IsAssignableFrom(type))
if (type.GetInterfaces()
.Any(x => x.IsGenericType && x.GetGenericTypeDefinition()
== typeof(IAggregateRoot<>)))
{
Type closedInsertCommandType = _openInsertCommandType.MakeGenericType(type);
Type closedInsertCommandHandlerType = _openInsertCommandHandlerType.MakeGenericType(type);
Type closedUpdateCommandType = _openUpdateCommandType.MakeGenericType(type);
Type closedUpdateCommandHandlerType = _openUpdateCommandHandlerType.MakeGenericType(type);
Type closedDeleteCommandType = _openDeleteCommandType.MakeGenericType(type);
Type closedDeleteCommandHandlerType = _openDeleteCommandHandlerType.MakeGenericType(type);
Type insertclosedHandlerInterfaceType = _openHandlerInterfaceType.MakeGenericType(closedInsertCommandType);
Type updateclosedHandlerInterfaceType = _openHandlerInterfaceType.MakeGenericType(closedUpdateCommandType);
Type deleteclosedHandlerInterfaceType = _openHandlerInterfaceType.MakeGenericType(closedDeleteCommandType);
registry.For(insertclosedHandlerInterfaceType).Use(closedInsertCommandHandlerType);
registry.For(updateclosedHandlerInterfaceType).Use(closedUpdateCommandHandlerType);
registry.For(deleteclosedHandlerInterfaceType).Use(closedDeleteCommandHandlerType);
}
}
}
And used it in my CompositionRoot:
public static class ApplicationConfiguration
{
public static IContainer Initialize()
{
ObjectFactory.Initialize(x =>
{
x.Scan(s =>
{
s.AssemblyContainingType(typeof(ICommandHandler<>));
s.AssemblyContainingType(typeof(Order));
s.AssemblyContainingType(typeof(FindOrderByIdQueryHandler));
s.WithDefaultConventions();
x.For(typeof(IUnitOfWork))
.Use(typeof(EfUnitOfWork<SaleDBContext>))
.Named("SaleDBContext")
.SetLifecycleTo((Lifecycles.Singleton));
s.Convention<CRUDCommandRegistrationConvention>();
});
});
return ObjectFactory.Container;
}
public static T Resolve<T>()
{
return ObjectFactory.GetInstance<T>();
}
}
I registered EfUnitOfWork<SaleDBContext> for IUnitOfWork, but I want to use separate DbContext per each module in my solution(Bounded context). For example my sale module has its own DbContext, HR module has its own DbContext and etc, and above registration conversion, only register EfUnitOfWork<SaleDBContext> as my IUnitOfWork.
I have some modules(Solution Folders in Visual Studio) in my solution and each module has 3 layer(3 class library projects):
My modules has following structure(each module has 3 assemblies) for example:
SaleModule:
----Application
----Domain (Entities , ...) //Order, Customer,...
----DAL (DbContext ,...) //SaleDbContext
HRModule:
----Application
----Domain (Entities , ...) // Employee, OrganizationUnit, ...
----DAL (DbContext ,...)//HRDbContext
InfrastructureModule:
----Application (ICommandHandler,IQueryHandler,...)
----Domain
----DAL
The InsertCommandHandler<T> puts in Infrastructure Module.
When I use the InsertCommanHandler<T> I want it uses corresponding module's DbContext as IUnitOfWork. for example, I want the InsertCommandHandler<Order> uses SaleDbContext as it's IUnitOfWork and InsertCommandHandler<Employee> uses HRDbContext as it's IUnitOfWork.
[UPDATED]
This is a sample of cunsumers code that IoC containar should provide SaleDbContext for Consumer1 and HRDbContext for Consumer2:
public class Consumer1
{
ICommandHandler<InsertCommandParameter<Order>> _insertCommandHandler;
public Consumer1(ICommandHandler<InsertCommandParameter<Order>> insertCommandHandler)
{
_insertCommandHandler = insertCommandHandler;
}
public void DoInsert()
{
var command = new InsertCommandParameter<Order>();
command.Entity = new Order(){
Number = 'ord-01',
// other properties
};
insertCommandHandler.Handle(command); //this query handler should use SaleDbContext
}
}
public class Consumer2
{
ICommandHandler<InsertCommandParameter<Employee>> _insertCommandHandler;
public Consumer2(ICommandHandler<InsertCommandParameter<Employee>> insertCommandHandler)
{
_insertCommandHandler = insertCommandHandler;
}
public void DoInsert()
{
var command = new InsertCommandParameter<Employee>();
command.Entity = new Employee(){
EmployeeNumber = 'Emp1',
// other properties
};
insertCommandHandler.Handle(command); //this query handler should use HRDbContext
}
}
How could I do that in my composition root using StructureMap?

You can make IUnitOfWork generic as in IUnitOfWork<TConnection>. This allows each Repository to stipulate which UnitOfWork it requires, ideally using constructor injection, e.g.
public class InsertCommandHandler : ICommandHandler<Order>
{
public InsertCommandHandler(IUnitOfWork<SalesDbContext> salesUnitOfWork)
{
// ...
}
}
However, you probably don't want to reference the DbContext in each handler so you should define an abstraction to avoid such a dependency.
Start with a simple interface that all DbContext wrapper classes will implement
public interface IConnection
{
DbContext Context { get; }
}
Update IUnitOfWork accordingly
public interface IUnitOfWork<TConnection> where TConnection : IConnection { }
Here's an example wrapper
public class SalesConnection : IConnection
{
private readonly DbContext context;
public SalesConnection()
{
this.context = new SalesDbContext();
}
public DbContext Context { get { return this.context; } }
}
And here's what the updated command handler will look like
public class InsertCommandHandler : ICommandHandler<Order>
{
public InsertCommandHandler(IUnitOfWork<SalesConnection> salesUnitOfWork)
{
// ...
}
}
UPDATE
The logical thing to do for common handlers is to have one per logical domain (i.e. per DbContext), for example SalesInsertCommandHandler, HRInsertCommandHandler
public class SalesInsertCommandHandler<TCommand> : ICommandHandler<TCommand>
{
public SalesInsertCommandHandler(IUnitOfWork<SalesConnection> unitOfWork)
{
}
}
This adheres to the separation of concerns principle and gives you extra flexibility when you come to decorate your concerns with different aspects (tracing, retry logic etc.)
All command handlers can of course inherit from a single common (abstract) command handler.
public abstract class CommandHandler<TConnection, TCommand> :
ICommandHandler<TCommand>
where TConnection : IConnection
{
private readonly IUnitOfWork<TConnection> unitOfWork;
public CommandHandler(IUnitOfWork<TConnection> unitOfWork)
{
this.unitOfWork = unitOfWork;
}
}
public class SalesInsertCommandHandler<TCommand> :
CommandHandler<SalesConnection, TCommand>
{
}

Constructor dependency injection via unity with parameters from HttpContext

We're using domain to customize how our application behaves. I'll illustrate it on example:
// default behavior
public class CoreService : IService {
public virtual string Hello { get { return "Hello"; } }
public virtual string FavouriteDrink { get { return "Water"; } }
}
// german.site.com
public class GermanService : CoreService {
public override string Hello { get { return "Gutten tag"; } }
public override string FavouriteDrink { get { return "Beer"; } }
}
// usa.site.com
public class UsaService : CoreService {
public override string FavouriteDrink { get { return "Cofee"; } }
}
Services are bootstrapped as follow:
var container = new UnityContainer();
container.RegisterType<IService, CoreService>();
container.RegisterType<IService, GermanService>("german.site.com");
container.RegisterType<IService, UsaService>("usa.site.com");
I use Unity to bootstrap mvc controllers. IE:
public class HomeController : Controller {
private IService m_Service;
// contructor dependency injection magic - this resolves into "CoreService"
public HomeController([Dependency]IService service) {
if (service == null) {
throw new ArgumentNullException("service");
}
m_Service = service;
}
}
Is there a way how to change unity resolution so it'll take domain into account ? Right now I ended up with
public class HomeController : Controller {
private IService m_Service;
// contructor dependency injection magic - a lot less magical
public HomeController() {
m_Service = DomainServiceLocator.Retrieve<IService>();
}
}
Support classes:
public static class DomainServiceLocator {
private static UnityContainerAdapter adapter;
public static T Retrieve<T>() {
string domain = HttpContext.Current.Request.Url.Host;
if (adapter.IsServiceRegistered(typeof(T), domain)) {
return adapter.Resolve<T>(domain);
}
return adapter.Resolve<T>();
}
}
public class QueryableContainerExtension : UnityContainerExtension {
private List<RegisterInstanceEventArgs> registeredInstances = new List<RegisterInstanceEventArgs>();
private List<RegisterEventArgs> registeredTypes = new List<RegisterEventArgs>();
protected override void Initialize() {
this.Context.Registering += (sender, e) => { this.registeredTypes.Add(e); };
this.Context.RegisteringInstance += (sender, e) => { this.registeredInstances.Add(e); };
}
public bool IsServiceRegistered(Type service, string name) {
return registeredTypes.FirstOrDefault(e => e.TypeFrom == service && e.Name == name) != null
|| registeredInstances.FirstOrDefault(e => e.RegisteredType == service && e.Name == name) != null;
}
}
public class UnityContainerAdapter {
private readonly QueryableContainerExtension queryableContainerExtension;
private readonly IUnityContainer unityContainer;
public UnityContainerAdapter()
: this(new UnityContainer()) {
}
public UnityContainerAdapter(IUnityContainer unityContainer) {
this.unityContainer = unityContainer;
// adding extensions to unity container
this.queryableContainerExtension = new QueryableContainerExtension();
unityContainer.AddExtension(this.queryableContainerExtension);
}
public T Resolve<T>(string name) {
return unityContainer.Resolve<T>(name);
}
public T Resolve<T>() {
return unityContainer.Resolve<T>();
}
public bool IsServiceRegistered(Type service, string name) {
return this.queryableContainerExtension.IsServiceRegistered(service, name);
}
}

I like to use an injection factory in these scenarios when resolving something at runtime. Essentially you're resolving your type via the domain name:
So in your composition root you could register like this:
container.RegisterType<Func<string, IService>>
(
new InjectionFactory(c => new Func<string, IService>(name => c.Resolve<IService>(name)))
);
Then in your HomeController you can inject the delegate
public class HomeController
{
private readonly Func<string,IService> _serviceFactory;
public HomeController(Func<string, IService> serviceFactory)
{
if(serviceFactory==null)
throw new ArgumentNullException("serviceFactory");
this._serviceFactory= serviceFactory;
}
public void DoSomethingWithTheService()
{
var domain = this.HttpContext.Uri.Host;
var service = this._serviceFactory(domain);
var greeting = service.Hello;
}
}
```
This is then still unit testable and you have not leaked the DI contain implementation outside of "composition root".
Also.. should CoreService be abstract to avoid direct instantiation of it?

Below is the solution I ended up with - it is based on #Spencer idea. I've created a factory, default implementation to the factory has a reference to DI container itself (IUnityContainer in my case), so it can perform the resolution based on domain once it is asked to. It is also more "modern friendly" since in current generation of ASP.NET (ASP.NET CORE) there is no such thing as magic singleton providing current HttpContext and DI is hard coded into the framework.
public interface IFactory<T>
{
T Retrieve(string domain);
}
internal sealed class Factory<T> : IFactory<T>
{
private readonly IUnityContainer _container;
public Factory(IUnityContainer container)
{
_container = container;
}
public T Resolve(string domain)
{
// this is actually more complex - we have chain inheritance here
// for simplicity assume service is either registered for given
// domain or it throws an error
return _container.Resolve<T>(domain);
}
}
// bootstrapper
var container = new UnityContainer();
container.RegisterType<IService, CoreService>();
container.RegisterType<IService, GermanService>("german.site.com");
container.RegisterType<IService, UsaService>("usa.site.com");
container.RegisterInstance<IFactory<IService>>(new Factory<IService>(container));
And the home controller looks like
public class HomeController : Controller {
private IFactory<IService> m_Factory;
public HomeController(IFactory<IService> factory) {
m_Factory = factory;
}
private void FooBar() {
var service = m_Factory.Retrieve(this.HttpContext.Uri.Host);
var hello = service.Hello;
}
}
Its also a worth mentioning that - as I'm lazy - I've build a system of decorative attributes like
[Domain("german.site.com")]
public class GermanService : IService { ... }
[DomainRoot]
public class CoreService : IService { ... }
[Domain("usa.site.com")]
public class UsaService : CoreService { ... }
So the bootstrapping is done automatically across all types in given assembly. But that part is a bit lengthy - if anyone is interested I can post it on github.