Nine.Injection

Nine.Injection is a portable lightweight constructor injection library for singleton objects.

Highlights

• Portable: Runs on Windows, Windows Phone 8, Windows Store, iOS, Android, etc.
• Always Singleton: Objects registered and resolved by the container are always singletons.
• Constructor Injection: Dependencies are expressed and injected by constructors only.

Installation

You can get Nine.Injection using NuGet:

Install-Package Nine.Injection

Getting Started

Dependencies are maintained by the Container

var container = new Container();

To map concrete implementations for an interface:

container.Map<IFoo, Foo>().Map<IFoo, Foo2>();

To map an existing instance for an interface:

container.Map<IFoo>(new Foo()).Map<IFoo>(new Foo2());

To map all public types that implements a specific interface:

container.MapAll<IFoo>(Assembly.GetExecutingAssembly());

To get the concrete implementation of an interface:

container.Get<IFoo>(); // Returns the last registered IFoo instance

To get all implementations that implements an interface:

container.GetAll<IFoo>(); // Returns all instances that implements IFoo

Objects get from the container are always singletons:

container.Map<IFoo, Foo>().Map<IFoo2, Foo>();
Assert.Equals(container.Get<IFoo>(), container.Get<IFoo>());
Assert.Equals(container.Get<IFoo>(), container.Get<IFoo2>());

Expressing Dependencies

Nine.Injection uses constructors to find dependencies:

public class UserService : IService
{
    public UserService(IStorage storage) { ... }
}

To instantiate UserService, a IStorage is resolved from the container and passed to the constructor of UserService.

If there are multiple arguments specified in the constructor, the one with the most arguments is used:

public UserService(IStorage storage)
public UserService(IStorage storage, ILogger logger) // This one is used

To inject all implementations of a given interface:

public ServiceContainer(params IService[] services)
public ServiceContainer(IEnumerable<IService> services)

In case of circular dependency, Lazy<> can be used to break the cyclic reference.

public UserService(Lazy<IStorage> storage)

Want to Learn More?

See the test specs to learn more about the behavior of Nine.Injection.