ServiceCollectionBuilder 0.1.1-beta

ServiceCollectionBuilder

Utility that helps to build the dependency graph used by interconnected services by using custom attributes, instead of maintaining a manual service configuration.

It integrates with Microsoft.Extensions.DependencyInjection by providing a IServiceCollection object pre configured with the dependant services.

Usage

Lest assume that our main component is the IHiFiveService interface.

public interface IHiFiveService
{
    int HiFive();
}

and it implementation details need a ILogger instance.

public class ServiceImpl : IHiFiveService
{

    private readonly ILogger _logger;

    public ServiceImpl(ILogger logger) {
        this._logger = logger;
    }

    public int HiFive()
    {
        _logger.debug("Sending HiFive");
        return 5;
    }
}

We can wire them up like

[ServiceImplementation(typeof(IHiFiveService))]
public class ServiceImpl : IHiFiveService{
    ...
}

[ServiceImplementation(typeof(ILogger))]
public class ConsoleLogger : ILogger {
    ...
}

and get a fully constructed IHiFiveService

IHiFiveService service = ServiceCollectionBuilder
    .FromCurrentAssembly()
    .BuildServiceProvider()
    .GetService<IHiFiveService>();

Components

Is possible to assign a component ID to each ServiceImplementation in order to group services that should work together. This way the same assembly can be used to supply instances of IServiceCollection with diffent services.

Scoped Contexts

One of the limitations I found with the current IServiceCollection is that the options pattern registers a Singleton service for context data.

Inspired by the same pattern ContextSpiBuilder can create Scoped IServiceProvider instances passing a different context instance every time.

Services can access the scope context by requiring a depedency of type IScopeCtx<T> where T is the context type.

public class Context
{
    public int Value { get; }

    public Context(int value = 0) { Value = value; }
}

[ServiceImplementation(typeof(ScopedService), scope:Attributes.Scope.Scoped, component:"scoped")]
public class ScopedService
{
    private readonly Context _context;

    public ScopedService(IScopeCtx<Context> context) { _context = context.Context; }

    public int GetContextValue() { return _context.Value; }
}

public void TestScopeBuilder()
{
    ContextSpiBuilder<Context> sb = ServiceCollectionBuilder.Create()
        .AddAssembly(Assembly.GetExecutingAssembly(), "scoped")
        .Context<Context>();

    var value1 = sb.CreateScope(new Context(123)).GetRequiredService<ScopedService>().GetContextValue();
    Assert.Equal(123, value1);
    
    var value2 = sb.CreateScope(new Context(999)).GetRequiredService<ScopedService>().GetContextValue();
    Assert.Equal(999, value2);
}

Changelog

v0.1.0-beta Initial beta release