Autofac: registering hierarchy of classes - autofac

Question

I am struggling to register with Autofac a hierarchy of classes and interfaces.
I have an interface IMyService defined as below:
public interface IMyService
{
void DoMyService();
}
And I have two abstract classes with implement this interface and called MyServiceA, and MyServiceB:
public abstract class MyServiceA : IMyService
{
public abstract DoMyService();
}
public abstract class MyServiceB : IMyService
{
public abstract DoMyService();
}
Moreover I have a second-level hierarchy for each of the two aforementioned services: MyServiceA1, MyServiceA2, MyServiceB1 and MyServiceB2:
public class MyServiceA1 : MyServiceA
{
public MyServiceA1() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
public class MyServiceA2 : MyServiceA
{
public MyServiceA2() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
public class MyServiceB1 : MyServiceB
{
public MyServiceB1() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
public class MyServiceB2 : MyServiceB
{
public MyServiceB2() : base() {}
public void DoMyService()
{
// Implementation goes here
}
}
I have in input two enums FirstEnum and SecondEnum used to select which of the four concrete types to instantiate:
public enum FirstEnum
{
SvcA,
SvcB
}
public enum SecondEnum
{
Svc1,
Svc2
}
I want to register IMyService and by providing two enums, It will automatically instantiate the good concrete type.
For instance, if I want to resolve an IMyService and I provide FirstEnum.SvcB and SecondEnum.Svc2, it should instantiate the concrete type MyServiceB2 class. Moreover this hierarchy might be updated by adding some other concrete types etc, so I need a generic way of doing it
Does anyone have a clue to help me?
Thanks

Answer 1

If you want to create a specific service dynamically depending on a set of parameters, this is a good use case for an abstract factory:
public interface IMyServiceFactory
{
IMyService Create(FirstEnum e1, SecondEnum e2);
}
public class MyServiceFactory : IMyServiceFactory
{
private readonly ILifetimeScope scope;
public MyServiceFactory(ILifetimeScope scope)
{
if (scope == null)
throw new ArgumentNullException("scope");
this.scope = scope;
}
public IMyService Create(FirstEnum e1, SecondEnum e2)
{
if (e1 == FirstEnum.SvcA)
{
if (e2 == SecondEnum.Svc1)
{
return scope.Resolve<MyServiceA1>();
}
else //svc2
{
return scope.Resolve<MyServiceA2>();
}
}
else //B
{
if (e2 == SecondEnum.Svc1)
{
return scope.Resolve<MyServiceB1>();
}
else //svc2
{
return scope.Resolve<MyServiceB2>();
}
}
}
}
And now your consumer need to get the factory injected instead of the service:
public class MyServiceConsumer
{
private readonly IMyServiceFactory factory;
public MyServiceConsumer(IMyServiceFactory factory)
{
this.factory = factory;
}
public void Do()
{
//var service = this.factory.Create
}
}
Registration :
Autofac.ContainerBuilder builder = new Autofac.ContainerBuilder();
builder.RegisterType<MyServiceA1>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceA2>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceB1>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceB2>().AsSelf().AsImplementedInterfaces();
builder.RegisterType<MyServiceFactory>().As<IMyServiceFactory>();
builder.RegisterType<MyServiceConsumer>();
//and quick test resolve
var container = builder.Build();
var test = container.Resolve<MyServiceConsumer>();