Introduction
In cases when you want to register a component only if (or unless) certain conditions are met, there are appropriate methods exposed in the API.
Registering component only if it was not registered previously:
container.Register(
Component.For(typeof(IRepository<>))
.ImplementedBy(typeof(Repository<>))
.OnlyNewServices()
);
Here we register component only if no component for
IRepository<> was previously registered.
Filtering components in multiple components registration
Corresponding methods are exposed also when registering multiple components:
container.Register(
Classes.Of<ICustomer>()
.FromAssembly(Assembly.GetExecutingAssembly())
.Unless(t => typeof(SpecificCustomer).IsAssignableFrom(t))
);
Here we register all types implementing ICustomer, except for SpecificCustomer and its descendants.
container.Register(
AllTypes.Of<ICustomer>()
.FromAssembly(Assembly.GetExecutingAssembly())
.If(t => t.FullName.Contains("Chain"))
);
For better readability multiple service registration exposes additional filtering methods
container.Register(
AllTypes.FromAssembly(Assembly.GetExecutingAssembly())
.Where(Component.IsInSameNamespaceAs<FooRepository>())
.WithService.FirstInterface()
);
You can also use Linq to do the filtering
\\
container.Register(
Classes.Of<CustomerChain1>()
.Pick(from type in Assembly.GetExecutingAssembly().GetExportedTypes()
where type.IsDefined(typeof(SerializableAttribute), true)
select type
)
);
Convention over Configuration
Notice what the above gives up - by virtue of putting a class in a specific namespace, inheriting from specific interface or having a specific attribute our components get registered and made available as services. We defined something very important here - conventions that free us from coding everything explicitly. This can't be overemphasized.
See also
Fluent Registration API