After migrating to .NET 6 RC 1 No service for type Microsoft.Extensions.Configuration.IConfiguration can be found

[marcuslindblom]

In my IServiceCollection extension I have this code.

var serviceProvider = services.BuildServiceProvider();
var configuration = serviceProvider.GetRequiredService<IConfiguration>();

This breaks ofter migrating to .NET 6 using the Program.cs only and no Startup class.
Do I need to register this in my extension as well? How can I make this work for .NET 5 and .NET 6?

[davidfowl]

Why is extension method building the IServiceProvider to get the IConfiguration?

[marcuslindblom]

@davidfowl In .NET 5, I thought I needed to?

[marcuslindblom]

So to be clear, this extension method is in a library I use both in .NET 5 and 6

[davidfowl]

Typically extension methods on IServiceCollection that need IConfiguration take in the user provided configuration via an argument. Building the service provider, builds a temporary throw away service provider and can results in a couple of problems:

• Multiple singleton instances
• Not disposing IDisposable services resolved when trying to resolve services from this temporary container.

Calling BuildServiceProvider is an anti-pattern because of those things.

That said, in this particular case of resolving IConfiguration, the side effects are usually fine since the host usually resolves the same singleton instance.

[marcuslindblom]

Ok, so it's ok to do this but it's an anti-pattern, right?

This is how I use the configuration and the arguments. From a best practice stand point, is it possible to make this code compliant with both .NET 5 and 6?

public static IServiceCollection AddStrife(this IServiceCollection services, Action<DocumentStoreOptions> configureOptions) {

    var serviceProvider = services.BuildServiceProvider();
    var configuration = serviceProvider.GetRequiredService<IConfiguration>();
    services.Configure<DocumentStoreOptions>(options => options.Settings = configuration.GetSection(nameof(DocumentStoreSettings))?.Get<DocumentStoreSettings>()).Configure(configureOptions)

    return services;
}

[davidfowl]

Like so.

public static IServiceCollection AddStrife(this IServiceCollection services, Action<DocumentStoreOptions> configureOptions)
{
    services.AddOptions<DocumentStoreOptions>()
            .Configure<IConfiguration>((options, configuration) =>
            {
                options.Settings = configuration.GetSection(nameof(DocumentStoreSettings))?.Get<DocumentStoreSettings>();
            })
            .Configure(configureOptions);

    return services;
}

cc @IEvangelist we have a doc for guidance on how to build these sorts of libraries now right?

[marcuslindblom]

Like so.

public static IServiceCollection AddStrife(this IServiceCollection services, Action<DocumentStoreOptions> configureOptions)
{
    services.AddOptions<DocumentStoreOptions>()
            .Configure<IConfiguration>((options, configuration) =>
            {
                options.Settings = configuration.GetSection(nameof(DocumentStoreSettings))?.Get<DocumentStoreSettings>();
            })
            .Configure(configureOptions);

    return services;
}

cc @IEvangelist we have a doc for guidance on how to build these sorts of libraries now right?

Ok, thanks. Changed my configuration to your proposed solution.

[davidfowl]

No problem. I'm gonna fix this anyway since it's a compatibility break.

[IEvangelist]

Like so.

public static IServiceCollection AddStrife(this IServiceCollection services, Action<DocumentStoreOptions> configureOptions)
{
    services.AddOptions<DocumentStoreOptions>()
            .Configure<IConfiguration>((options, configuration) =>
            {
                options.Settings = configuration.GetSection(nameof(DocumentStoreSettings))?.Get<DocumentStoreSettings>();
            })
            .Configure(configureOptions);

    return services;
}

cc @IEvangelist we have a doc for guidance on how to build these sorts of libraries now right?

Yes sir, here you are @davidfowl

✔️ Options pattern guidance for .NET library authors