ProviderAttribute

NexusLabs.Needlr.Generators

ProviderAttribute Class

Marks an interface or partial class as a Provider - a strongly-typed service locator.

public sealed class ProviderAttribute : System.Attribute

Inheritance System.Object 🡒 System.Attribute 🡒 ProviderAttribute

Remarks

A Provider is a compile-time generated class that provides strongly-typed access to services registered in the dependency injection container. Unlike using IServiceProvider.GetService<T>() directly, Providers offer: - Compile-time verification that required services are registered - IntelliSense and IDE support for available services - Easy mocking in unit tests

Providers are always registered as Singletons. All service properties are resolved via constructor injection at Provider construction time (fail-fast). For creating new instances on demand, use the Factories parameter to generate factory properties.

Usage modes: 1. Interface definition: Apply to an interface with get-only properties. The generator creates an implementing class.

[Provider]
public interface IOrderServicesProvider
{
    IOrderRepository Repository { get; }
    IOrderValidator Validator { get; }
}
// Generates: OrderServicesProvider class

2. Shorthand class: Apply to a partial class with type parameters. The generator creates both an interface and the implementation.

[Provider(typeof(IOrderRepository), typeof(IOrderValidator))]
public partial class OrderDependenciesProvider { }
// Generates: IOrderDependenciesProvider interface + implementation

Constructors

ProviderAttribute() Constructor

Creates a Provider attribute for an interface definition. Define service properties directly on the interface.

public ProviderAttribute();

ProviderAttribute(Type[]) Constructor

Creates a Provider with the specified required service types. Use on a partial class to auto-generate interface and implementation.

public ProviderAttribute(params System.Type[] requiredServices);

Parameters

requiredServices System.Type[]

Service types that must be registered in the container. Property names are derived from type names (e.g., IOrderRepository → OrderRepository).

Properties

ProviderAttribute.Collections Property

Service types to resolve as IEnumerable<T>.

public System.Type[]? Collections { get; set; }

Property Value

System.Type[]

Remarks

Properties for these services use GetServices<T>() and return all registered implementations.

ProviderAttribute.Factories Property

Types to generate factories for, enabling creation of new instances.

public System.Type[]? Factories { get; set; }

Property Value

System.Type[]

Remarks

For each type specified: - If the type has [GenerateFactory], the existing factory is used. - Otherwise, a factory (IXxxFactory) is generated automatically.

This allows the Provider to create new instances while remaining a Singleton.

ProviderAttribute.Optional Property

Service types that may not be registered. Properties are nullable.

public System.Type[]? Optional { get; set; }

Property Value

System.Type[]

Remarks

Properties for these services use GetService<T>() and return null if the service is not registered.

ProviderAttribute.Required Property

Service types that must be registered. Resolution failure throws at startup.

public System.Type[]? Required { get; set; }

Property Value

System.Type[]

Remarks

Properties for these services use GetRequiredService<T>(). If any service is not registered, the application fails to start.