shinyorg/shiny-di

Shiny Dependency Injection Skill

Triggers

• ServiceAttribute
• SingletonAttribute
• ScopedAttribute
• TransientAttribute
• AddShinyServiceRegistry
• AddGeneratedServices
• AddSingletonAsImplementedInterfaces
• AddScopedAsImplementedInterfaces
• Shiny.Extensions.DependencyInjection

You are an expert in Shiny Extensions Dependency Injection, a .NET library providing attribute-driven service registration with source generators.

When to Use This Skill

Invoke this skill when the user wants to:

• Register services using [Singleton], [Scoped], or [Transient] attributes with source generation
• Configure the Shiny DI service registry in their application
• Use keyed services, categories, TryAdd semantics
• Register services against multiple interfaces
• Use open generics with DI attributes

Library Overview

Documentation: https://shinylib.net/extensions/di/ Repository: https://github.com/shinyorg/Shiny.Extensions Package: Shiny.Extensions.DependencyInjection Namespace: Shiny

Registration Attributes

Mark classes with attributes for automatic DI registration via source generation:

[Singleton]                                    // Singleton lifetime
public class MyService : IMyService { }

[Scoped]                                       // Scoped lifetime
public class MyRepository : IRepository { }

[Transient]                                    // Transient lifetime
public class MyFactory : IFactory { }

Attribute Properties

All registration attributes support these properties:

| Property | Type | Description | |----------|------|-------------| | AsSelf | bool | Register as the class itself rather than its interface | | Type | Type | Register against a specific interface (when class implements multiple) | | KeyedName | string? | Register as a keyed service | | Category | string? | Category for conditional registration | | TryAdd | bool | Use TryAdd semantics (won't replace existing registrations) |

Examples

// Register as the class itself
[Singleton(AsSelf = true)]
public class AppState { }

// Register against a specific interface
[Singleton(Type = typeof(ISpecificInterface))]
public class MultiInterfaceService : ISpecificInterface, IOtherInterface { }

// Keyed service
[Singleton(KeyedName = "primary")]
public class PrimaryCache : ICache { }

// Category-based conditional registration
[Singleton(Category = "premium")]
public class PremiumFeature : IFeature { }

// TryAdd semantics
[Singleton(TryAdd = true)]
public class DefaultLogger : ILogger { }

Setup

// Register all source-generated services
builder.Services.AddShinyServiceRegistry();

// Register with specific categories only
builder.Services.AddShinyServiceRegistry("premium", "analytics");

Helper Extensions

// Register a singleton against all implemented interfaces
services.AddSingletonAsImplementedInterfaces<MyService>();
services.AddSingletonAsImplementedInterfaces<MyService>("keyName");

// Register scoped against all implemented interfaces
services.AddScopedAsImplementedInterfaces<MyService>();

// Check registrations
bool hasService = services.HasService<IMyService>();
bool hasImpl = services.HasImplementation<MyService>();

// Lazy resolution
Lazy<IMyService> lazy = services.GetLazyService<IMyService>(required: true);

Code Generation Instructions

• Always use attributes ([Singleton], [Scoped], [Transient]) over manual registration
• Choose appropriate lifetime: Singleton for stateless services, Scoped for per-request (DbContext), Transient for lightweight factories
• Use Category for optional features that may not always be registered
• Use KeyedName when multiple implementations of the same interface exist
• Always call AddShinyServiceRegistry() to activate source-generated registrations

Best Practices

1. Use source generation - Always prefer [Singleton]/[Scoped]/[Transient] attributes over manual services.Add*() calls
2. Call AddShinyServiceRegistry() - Required to activate source-generated registrations
3. Appropriate lifetimes - Singleton for stateless, Scoped for DbContext/unit-of-work, Transient for factories
4. Use keyed services - When multiple implementations exist, use KeyedName to disambiguate