Injectio

Source generator that helps register attribute marked services in the dependency injection ServiceCollection

Features

• Transient, Singleton, Scoped service registration
• Factory registration
• Module method registration
• Duplicate Strategy - Skip,Replace,Append
• Registration Strategy - Self, Implemented Interfaces, Self With Interfaces

Usage

Add package

Add the nuget package project to your projects.

dotnet add package Injectio

Prevent dependances from including Injectio

<PackageReference Include="Injectio" PrivateAssets="all" />

Registration Attributes

Place registration attribute on class. The class will be discovered and registered.

• [RegisterSingleton] Marks the class as a singleton service
• [RegisterScoped] Marks the class as a scoped service
• [RegisterTransient] Marks the class as a transient service
• [RegisterServices] Marks the method to be called to register services

Attribute Properties

Property	Description
ImplementationType	The type that implements the service. If not set, the class the attribute is on will be used.
ServiceType	The type of the service. If not set, the Registration property used to determine what is registered.
Factory	Name of a factory method to create new instances of the service implementation.
Duplicate	How the generator handles duplicate registrations. See Duplicate Strategy
Registration	How the generator determines what to register. See Registration Strategy

Duplicate Strategy

Value	Description
Skip	Skips registrations for services that already exists
Replace	Replaces existing service registrations
Append	Appends a new registration for existing services

Registration Strategy

Value	Description
Self	Registers each matching concrete type as itself
ImplementedInterfaces	Registers each matching concrete type as all of its implemented interfaces
SelfWithInterfaces	Registers each matching concrete type as all of its implemented interfaces and itself

Singleton services

[RegisterSingleton]
public class SingletonService : IService { }

Explicit service type

[RegisterSingleton(ServiceType = typeof(IService))]
public class SingletonService : IService { }

Support resolving multiple services with IEnumerable<T>

[RegisterSingleton(Duplicate = DuplicateStrategy.Append)]
public class SingletonService : IService { }

Scoped Services

[RegisterScoped]
public class ScopedService : IService { }

Transient Services

[RegisterTransient]
public class TransientService : IService { }

Factories

[RegisterTransient(Factory = nameof(ServiceFactory))]
public class FactoryService : IFactoryService
{
    private readonly IService _service;

    public FactoryService(IService service)
    { 
        _service = service;
    }

    public static IFactoryService ServiceFactory(IServiceProvider serviceProvider)
    {
        return new FactoryService(serviceProvider.GetService<IService>());
    }
}

Open Generic

[RegisterSingleton(ImplementationType = typeof(OpenGeneric<>), ServiceType = typeof(IOpenGeneric<>))]
public class OpenGeneric<T> : IOpenGeneric<T> { }

Generic Attributes

You can use generic attributes to register services if your project targets .NET 7.0+

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFrameworks>net7.0</TargetFrameworks>
  </PropertyGroup>
</Project>

Generic attributes allow declaration to be more compact by avoiding the typeof calls

[RegisterSingleton<IService>]
public class ServiceImplementation : IService { }

Keyed Services

You can register keyed services with version 8.0+ of Microsoft.Extensions.DependencyInjection

Register a keyed service

[RegisterSingleton<IServiceKeyed>(ServiceKey = "Alpha")]
public class ServiceAlphaKeyed : IServiceKeyed
{
}

[RegisterSingleton<IServiceKeyed>(ServiceKey = "Beta")]
public class ServiceBetaKeyed : IServiceKeyed
{
}

Register using an enum

public enum ServiceType
{
    Alpha,
    Beta
}

[RegisterSingleton<IServiceKeyed>(ServiceKey = ServiceType.Alpha)]
public class ServiceAlphaTypeKeyed : IServiceKeyed
{
}

[RegisterSingleton<IServiceKeyed>(ServiceKey = ServiceType.Beta)]
public class ServiceBetaTypeKeyed : IServiceKeyed
{
}

Register using an factory method

[RegisterSingleton<IServiceKeyed>(ServiceKey = "Charlie", Factory = nameof(ServiceFactory))]
[RegisterSingleton<IServiceKeyed>(ServiceKey = "Delta", Factory = nameof(ServiceFactory))]
public class ServiceFactoryKeyed : IServiceKeyed
{
    public ServiceFactoryKeyed(object? serviceKey)
    {
        ServiceKey = serviceKey;
    }

    public object? ServiceKey { get; }

    public static IServiceKeyed ServiceFactory(IServiceProvider serviceProvider, object? serviceKey)
    {
        return new ServiceFactoryKeyed(serviceKey);
    }

}

Register Method

When the service registration is complex, use the RegisterServices attribute on a method that has a parameter of IServiceCollection or ServiceCollection

public class RegistrationModule
{
    [RegisterServices]
    public static void Register(IServiceCollection services)
    {
        // add and bind configuration options, Microsoft.Extensions.Configuration.Binder
        services
            .AddOptions<PollingOption>()
            .Configure<IConfiguration>((settings, configuration) => configuration
                .GetSection(PollingOption.SectionName)
                .Bind(settings)
            );
    }
}

Add to container

The source generator creates an extension method with all the discovered services registered. Call the generated extension method to add the services to the container. The extension method will be called Add[AssemblyName]. The assembly name will have the dots removed.

var services = new ServiceCollection();
services.AddInjectioTestsConsole();

Override the extension method name by using the InjectioName MSBuild property.

<PropertyGroup>
  <InjectioName>Library</InjectioName>
</PropertyGroup>
<ItemGroup>
 <CompilerVisibleProperty Include="InjectioName" />
</ItemGroup>

var services = new ServiceCollection();
services.AddLibrary();

Registration Tags

Control what is registered when calling the generated extension method using Tags

Tag the service

public interface IServiceTag
{
}

[RegisterSingleton(Tags = "Client,FrontEnd")]
public class ServiceTag : IServiceTag
{
}

Tags can be passed to register methods

public static class ServiceRegistration
{
    [RegisterServices]
    public static void Register(IServiceCollection services, ISet<string> tags)
    {

    }
}

Specify tags when adding to service collection. Note, if no tags specified, all services are registered

var services = new ServiceCollection();
services.AddInjectioTestsLibrary("Client");