In my application, I have a service that requires a constructor parameter not resolved by Autofac, that I instantiate using a delegate factory:
public class Service
{
public Service(string parameter /*, ... other dependencies */)
{
}
public delegate Service Factory(string parameter);
}
This works great! I really love this feature.
I also like the Controlled Lifetime relationship, so I can let my component depend on a Func<Owned<ISomething>> like this:
public class Component
{
private Func<Owned<ISomething>> _somethingFactory;
/* constructor omitted for brevity */
public void DoSomethingUseful()
{
using (var ownedSomething = _somethingFactory())
{
/* Lots of useful code here */
}
}
}
My problem is that now I want to combine the two. I can't have an instance of Func<Owned<Service>> injected, because it needs that parameter, so my current solution is to abstract the factory away into another service, say IServiceFactory:
public interface IServiceFactory
{
Service Create(string parameter);
}
...implemented as such:
public class ServiceFactory : IServiceFactory
{
private Service.Factory _internalFactory;
public ServiceFactory(Service.Factory internalFactory)
{
_internalFactory = internalFactory;
}
public Service Create(string parameter)
{
return _internalFactory(parameter);
}
}
My component then becomes this:
public class Component
{
Func<Owned<IServiceFactory>> _serviceFactoryFactory;
/* ... */
}
The need for such a field name leaves a bad taste in my mouth to the point that I suspect there must be a cleaner way to handle this case.
Is there another way?
You could change your injected factory to include the string parameter:
private Func<string, Owned<ISomething>> _somethingFactory;
Then you can pass the string to the factory when you want to create a new instance:
public void DoSomethingUseful()
{
using (var ownedSomething = _somethingFactory("my parameter"))
{
/* Lots of useful code here */
}
}
I've created a .NET Fiddle with a small working sample.
I am trying to setup interface method that will give version number:
var versionNumber = System.Reflection.Assembly.GetExecutingAssembly().GetName().Version.ToString();
I am not sure how to implement this in an interface, so that the inheriting class can get the version number?
public interface IVersionProvider
{
string GetVersion();
}
implementation:
internal class /*or struct*/ VersionProvider : IVersionProvider
{
public string GetVersion()
{
System.Reflection.Assembly.GetExecutingAssembly()
.GetName().Version.ToString();
}
}
I made the class internal, because it doesn't need to be externally creatable:
public class Factory
{
IVersionProvider GetVersionProvider() { return new VersionProvider(); }
}
Since the interface is public, external users will be able to call 'GetVersion' on it even though the implementation is private to the assembly.
I am trying to configure an application such that types from assemblyA can be used by my console to allow for logging in an AOP style. The JournalInterceptor will just write out method calls, input and maybe output arguments to a log file or datastore of some kind.
I can register one type at a time but I would like to register all types in one go. Once I get going I may add some filtering to the registered types but I am missing something.
I am trying to use Classes.FromAssemblyContaining but am not sure how to get at an IRegistration instance for the call to WindsorContainer::Register
Any clues?
// otherAssembly.cs
namespace assemblyA
{
public class Foo1 { public virtual void What(){} }
public class Foo2 { public virtual void Where(){} }
}
// program.cs
namespace console
{
using assemblyA;
public class JournalInterceptor : IInterceptor {}
public class Program
{
public static void Main()
{
var container = new Castle.Windsor.WindsorContainer()
.Register(
Component.For<JournalInterceptor>().LifeStyle.Transient,
// works but can't be the best way
Component.For<Foo1>().LifeStyle.Transient
.Interceptors<JournalInterceptor>(),
Component.For<Foo2>().LifeStyle.Transient,
.Interceptors<JournalInterceptor>(),
// how do I do it this way
Classes.FromAssemblyContaining<Foo1>()
.Pick()
.LifestyleTransient()
.Interceptors<JournalInterceptor>()
);
Foo1 foo = container.Resolve<Foo1>();
}
}
}
Implement a Pointcut. In Castle Windsor this is done by implementing the IModelInterceptorsSelector interface.
It would go something like this:
public class JournalPointcut : IModelInterceptorsSelector
{
public bool HasInterceptors(ComponentModel model)
{
return true; // intercept everything - probably not a good idea, though
}
public InterceptorReference[] SelectInterceptors(
ComponentModel model, InterceptorReference[] interceptors)
{
return new[]
{
InterceptorReference.ForType<JournalInterceptor>()
}.Concat(interceptors).ToArray();
}
}
Then register the Interceptor and the Pointcut with the container:
this.container.Register(Component.For<JounalInterceptor>());
this.container.Kernel.ProxyFactory.AddInterceptorSelector(new JournalPointcut());
For in-depth explanation, you may want to see this recording.
I'm using StructureMap to resolve references to my repository class. My repository interface implements IDisposable, e.g.
public interface IMyRepository : IDisposable
{
SomeClass GetById(int id);
}
An implementation of the interface using Entity Framework:
public MyRepository : IMyRepository
{
private MyDbContext _dbContext;
public MyDbContext()
{
_dbContext = new MyDbContext();
}
public SomeClass GetById(int id)
{
var query = from x in _dbContext
where x.Id = id
select x;
return x.FirstOrDefault();
}
public void Dispose()
{
_dbContext.Dispose();
}
}
Anyway as mentioned I'm using StructureMap to resolve IMyRepository. So when, where and how should I call my dispose method?
WARNING: please note that my views have changed, and you should consider the following advise outdated. Please see this answer for an updated view: https://stackoverflow.com/a/30287923/264697
While DI frameworks can manage lifetime of objects for you and some could even dispose objects for you after you're done using with them, it makes object disposal just too implicit. The IDisposable interface is created because there was the need of deterministic clean-up of resources. Therefore, in the context of DI, I personally like to make this clean-up very explicit. When you make it explicit, you've got basically two options: 1. Configure the DI to return transient objects and dispose these objects yourself. 2. Configure a factory and instruct the factory to create new instances.
I favor the second approach over the first, because especially when doing Dependency Injection, your code isn't as clean as it could be. Look for instance at this code:
public sealed class Client : IDisposable
{
private readonly IDependency dependency;
public Client(IDependency dependency)
{
this. dependency = dependency;
}
public void Do()
{
this.dependency.DoSomething();
}
public Dispose()
{
this.dependency.Dispose();
}
}
While this code explicitly disposes the dependency, it could raise some eyebrows to readers, because resources should normally only be disposed by the owner of the resource. Apparently, the Client became the owner of the resource, when it was injected.
Because of this, I favor the use of a factory. Look for instance at this example:
public sealed class Client
{
private readonly IDependencyFactory factory;
public Client(IDependencyFactory factory)
{
this.factory = factory;
}
public void Do()
{
using (var dependency = this.factory.CreateNew())
{
dependency.DoSomething();
}
}
}
This example has the exact same behavior as the previous example, but see how the Client class doesn't have to implement IDisposable anymore, because it creates and disposes the resource within the Do method.
Injecting a factory is the most explicit way (the path of least surprise) to do this. That's why I prefer this style. Downside of this is that you often need to define more classes (for your factories), but I personally don't mind.
RPM1984 asked for a more concrete example.
I would not have the repository implement IDisposable, but have a Unit of Work that implements IDisposable, controls/contains repositories and have a factory that knows how to create new unit of works. With that in mind, the above code would look like this:
public sealed class Client
{
private readonly INorthwindUnitOfWorkFactory factory;
public Client(INorthwindUnitOfWorkFactory factory)
{
this.factory = factory;
}
public void Do()
{
using (NorthwindUnitOfWork db =
this.factory.CreateNew())
{
// 'Customers' is a repository.
var customer = db.Customers.GetById(1);
customer.Name = ".NET Junkie";
db.SubmitChanges();
}
}
}
In the design I use, and have described here, I use a concrete NorthwindUnitOfWork class that wraps an IDataMapper that is the gateway to the underlying LINQ provider (such as LINQ to SQL or Entity Framework). In sumary, the design is as follows:
An INorthwindUnitOfWorkFactory is injected in a client.
The particular implementation of that factory creates a concrete NorthwindUnitOfWork class and injects a O/RM specific IDataMapper class into it.
The NorthwindUnitOfWork is in fact a type-safe wrapper around the IDataMapper and the NorthwindUnitOfWork requests the IDataMapper for repositories and forwards requests to submit changes and dispose to the mapper.
The IDataMapper returns Repository<T> classes and a repository implements IQueryable<T> to allow the client to use LINQ over the repository.
The specific implementation of the IDataMapper holds a reference to the O/RM specific unit of work (for instance EF's ObjectContext). For that reason the IDataMapper must implement IDisposable.
This results in the following design:
public interface INorthwindUnitOfWorkFactory
{
NorthwindUnitOfWork CreateNew();
}
public interface IDataMapper : IDisposable
{
Repository<T> GetRepository<T>() where T : class;
void Save();
}
public abstract class Repository<T> : IQueryable<T>
where T : class
{
private readonly IQueryable<T> query;
protected Repository(IQueryable<T> query)
{
this.query = query;
}
public abstract void InsertOnSubmit(T entity);
public abstract void DeleteOnSubmit(T entity);
// IQueryable<T> members omitted.
}
The NorthwindUnitOfWork is a concrete class that contains properties to specific repositories, such as Customers, Orders, etc:
public sealed class NorthwindUnitOfWork : IDisposable
{
private readonly IDataMapper mapper;
public NorthwindUnitOfWork(IDataMapper mapper)
{
this.mapper = mapper;
}
// Repository properties here:
public Repository<Customer> Customers
{
get { return this.mapper.GetRepository<Customer>(); }
}
public void Dispose()
{
this.mapper.Dispose();
}
}
What's left is an concrete implementation of the INorthwindUnitOfWorkFactory and a concrete implementation of the IDataMapper. Here's one for Entity Framework:
public class EntityFrameworkNorthwindUnitOfWorkFactory
: INorthwindUnitOfWorkFactory
{
public NorthwindUnitOfWork CreateNew()
{
var db = new ObjectContext("name=NorthwindEntities");
db.DefaultContainerName = "NorthwindEntities";
var mapper = new EntityFrameworkDataMapper(db);
return new NorthwindUnitOfWork(mapper);
}
}
And the EntityFrameworkDataMapper:
public sealed class EntityFrameworkDataMapper : IDataMapper
{
private readonly ObjectContext context;
public EntityFrameworkDataMapper(ObjectContext context)
{
this.context = context;
}
public void Save()
{
this.context.SaveChanges();
}
public void Dispose()
{
this.context.Dispose();
}
public Repository<T> GetRepository<T>() where T : class
{
string setName = this.GetEntitySetName<T>();
var query = this.context.CreateQuery<T>(setName);
return new EntityRepository<T>(query, setName);
}
private string GetEntitySetName<T>()
{
EntityContainer container =
this.context.MetadataWorkspace.GetEntityContainer(
this.context.DefaultContainerName, DataSpace.CSpace);
return (
from item in container.BaseEntitySets
where item.ElementType.Name == typeof(T).Name
select item.Name).First();
}
private sealed class EntityRepository<T>
: Repository<T> where T : class
{
private readonly ObjectQuery<T> query;
private readonly string entitySetName;
public EntityRepository(ObjectQuery<T> query,
string entitySetName) : base(query)
{
this.query = query;
this.entitySetName = entitySetName;
}
public override void InsertOnSubmit(T entity)
{
this.query.Context.AddObject(entitySetName, entity);
}
public override void DeleteOnSubmit(T entity)
{
this.query.Context.DeleteObject(entity);
}
}
}
You can find more information about this model here.
UPDATE December 2012
This an an update written two years after my original answer. The last two years much has changed in the way I try to design the systems I'm working on. Although it has suited me in the past, I don't like to use the factory approach anymore when dealing with the Unit of Work pattern. Instead I simply inject a Unit of Work instance into consumers directly. Whether this design is feasibly for you however, depends a lot on the way your system is designed. If you want to read more about this, please take a look at this newer Stackoverflow answer of mine: One DbContext per web request…why?
If you want to get it right, i'd advise on a couple of changes:
1 - Don't have private instances of the data context in the repository. If your working with multiple repositories then you'll end up with multiple contexts.
2 - To solve the above - wrap the context in a Unit of Work. Pass the unit of work to the Repositories via the ctor: public MyRepository(IUnitOfWork uow)
3 - Make the Unit of Work implement IDisposable. The Unit of Work should be "newed up" when a request begins, and therefore should be disposed when the request finishes. The Repository should not implement IDisposable, as it is not directly working with resources - it is simply mitigating them. The DataContext / Unit of Work should implement IDispoable.
4 - Assuming you are using a web application, you do not need to explicitly call dispose - i repeat, you do not need to explicitly call your dispose method. StructureMap has a method called HttpContextBuildPolicy.DisposeAndClearAll();. What this does is invoke the "Dispose" method on any HTTP-scoped objects that implement IDisposable. Stick this call in Application_EndRequest (Global.asax). Also - i believe there is an updated method, called ReleaseAllHttpScopedObjects or something - can't remember the name.
Instead of adding Dispose to IMyRepository, you could declare IMyRepository like this:
public interface IMyRepository: IDisposable
{
SomeClass GetById(int id);
}
This way, you ensure all repository will call Dispose sometimes, and you can use the C# "using" pattern on a Repository object:
using (IMyRepository rep = GetMyRepository(...))
{
... do some work with rep
}
We currently have a suite of integration tests that run via MbUnit test suites. We are in the process of refactoring much of the code to use an IOC framework (StructureMap).
I'd like to configure/initialize the container ONCE when the MBUnit test runner fires up, using the same registry code that we use in production.
Is there a way of achieving this in MbUnit?
(EDIT) The version of MbUnit is 2.4.197.
Found it. The AssemblyCleanup attribute.
http://www.testingreflections.com/node/view/639
I understand that you want to spin up only one container for your entire test run and have it be the container used across test suite execution. The MBUnit docs make it look like you might be able to use a TestSuiteFixture and TestSuiteFixtureSetup to accomplish about what you want.
I wanted to speak from the point of view of a StructureMap user and Test Driven Developer.
We rarely use containers in our test suites unless we are explicitly testing pulling things out of the container. When this is necessary I use the an abstract test base class below (warning we use NUnit):
[TestFixture]
public abstract class with_container
{
protected IContainer Container;
[TestFixtureSetUp]
public void beforeAll()
{
Container = new ServiceBootstraper().GetContainer();
Container.AssertConfigurationIsValid();
}
}
public class Bootstraper
{
public Bootstraper()
{
ObjectFactory.Initialize(x =>
{
//register stuff here
});
}
public IContainer GetContainer()
{
return ObjectFactory.Container;
}}
I would recommend for normal tests that you skip the normal container and just use the automocking container included with StructureMap. Here is another handy abstract test base class we use.
public abstract class Context<T> where T : class
{
[SetUp]
public void Setup()
{
_services = new RhinoAutoMocker<T>(MockMode.AAA);
OverrideMocks();
_cut = _services.ClassUnderTest;
Given();
}
public RhinoAutoMocker<T> _services { get; private set; }
public T _cut { get; private set; }
public SERVICE MockFor<SERVICE>() where SERVICE : class
{
return _services.Get<SERVICE>();
}
public SERVICE Override<SERVICE>(SERVICE with) where SERVICE : class
{
_services.Inject(with);
return with;
}
public virtual void Given()
{
}
public virtual void OverrideMocks()
{
}
}
and here is a basic test using this context tester:
[TestFixture]
public class communication_publisher : Context<CommunicationPublisher>
{
[Test]
public void should_send_published_message_to_endpoint_retrieved_from_the_factory()
{
var message = ObjectMother.ValidOutgoingCommunicationMessage();
_cut.Publish(message);
MockFor<IEndpoint>().AssertWasCalled(a => a.Send(message));
}
}
Sorry if this is not exactly what you wanted. Just these techniques work very well for us and I wanted to share.