Question about scopes and providers

[sungam3r]

I have been working with DI for quite some time but still don’t understand some things.

Given that example:

namespace test
{
    [TestFixture]
    internal class ScopeTest
    {
        private IServiceProvider _provider;
        private IServiceProvider _temp;

        interface IAaa
        {

        }

        class AAA : IAaa
        {

        }

        interface Ibbb
        {

        }

        class BBB : Ibbb
        {

        }

        interface Iccc
        {

        }

        class CCC : Iccc
        {

        }

        [OneTimeSetUp]
        public void Setup()
        {
            var services = new ServiceCollection()
                .AddScoped<AAA>()
                .AddSingleton<BBB>()
                .AddTransient<CCC>()
                .AddScoped<IAaa>(prov =>
                {
                    if (ReferenceEquals(prov, _provider))
                        Console.WriteLine("rootA");
                    else if (ReferenceEquals(prov, _temp))
                        Console.WriteLine("scopeA");
                    else
                        Console.WriteLine("unknownA");
                    return prov.GetRequiredService<AAA>();
                })
                .AddSingleton<Ibbb>(prov =>
                {
                    if (ReferenceEquals(prov, _provider))
                        Console.WriteLine("rootB");
                    else if (ReferenceEquals(prov, _temp))
                        Console.WriteLine("scopeB");
                    else
                        Console.WriteLine("unknownB");
                    return prov.GetRequiredService<BBB>();
                })
                .AddTransient<Iccc>(prov =>
                {
                    if (ReferenceEquals(prov, _provider))
                        Console.WriteLine("rootC");
                    else if (ReferenceEquals(prov, _temp))
                        Console.WriteLine("scopeC");
                    else
                        Console.WriteLine("unknownC");
                    return prov.GetRequiredService<CCC>();
                });
            _provider = services.BuildServiceProvider(validateScopes: true);
        }

        [Test]
        public void Hhh()
        {
            using (var fff = _provider.CreateScope())
            {
                _temp = fff.ServiceProvider;
                var ttt1 = fff.ServiceProvider.GetRequiredService<IAaa>();
                var ttt2 = fff.ServiceProvider.GetRequiredService<Ibbb>();
                var ttt3 = fff.ServiceProvider.GetRequiredService<Iccc>();
            }
        }
    }
}

I get this result:

scopeA
unknownB      <-- ???
scopeC

What is the reason for this behavior?

[javiercn]

@sungam3r thanks for contacting us.

@anurse is platform the right area for these types of things?

[davidfowl]

@javiercn it belongs in extensions and eventually runtime.

What is the reason for this behavior?

It's an internal implementation detail of the service provider. The top level service provider instance isn't the same instance given to you when you resolve singleton services but it is backed by the same data.

We hand the call back an ServiceProviderEngineScope vs the top level ServiceProvider instance.

[sungam3r]

but it is backed by the same data

Do you mean that both instances share the same set of resolved services?

[davidfowl]

Yes

[analogrelay]

Transferred to dotnet/extensions.

[analogrelay]

Sounds like the question has been answered. Closing.