IOptions extension method to bind both IOptions<T> and T as a singleton

OptionsExtension.cs

public static class OptionsExtensions
{
    public static IServiceCollection ConfigureOptionsAndInstance<T>(this IServiceCollection services, IConfigurationSection section)
        where T : class, IOptions<T>, new()
    {
        services.Configure<T>(section);
        services.AddSingleton<T>(provider => provider.GetService<IOptions<T>>().Value);

        return services;
    }
}

public class S3Configuration : IOptions<S3Configuration>
{
    public string SecretKey { get; set; }

    [JsonIgnore]
    public S3Configuration Value => this;
}

// Example DI configuration
public class DependencyInjection
{
    public static void ConfigureServices(IServiceCollection services, IConfigurationRoot configurationRoot)
    {
        services.AddOptions();
        services.ConfigureOptionsAndInstance<S3Configuration>(configurationRoot.GetSection("S3"));
    }
}

// Example test case
[Fact]
public void Test1()
{
    // given
    var configurationBuilder = new ConfigurationBuilder();
    configurationBuilder.AddInMemoryCollection(new Dictionary<string, string>
    {
        { "S3:SecretKey", "123" }
    });

    var serviceCollection = new ServiceCollection();
    var configurationRoot = configurationBuilder.Build();

    // when
    DependencyInjection.ConfigureServices(serviceCollection, configurationRoot);

    // then
    ServiceProvider provider = services.BuildServiceProvider();
    var s3Options = provider.GetService<IOptions<S3Configuration>>();
    var s3Config = provider.GetService<S3Configuration>();

    s3Options.ShouldNotBeNull();
    s3Options.Value.ShouldNotBeNull();
    s3Options.Value.SecretKey.ShouldBe("123");
    s3Options.Value.AccessKey.ShouldBe("999");
    s3Options.Value.Region.ShouldBe("eu-west-1");

    s3Config.ShouldNotBeNull();
    s3Config.SecretKey.ShouldBe("123");
    s3Config.AccessKey.ShouldBe("999");
    s3Config.Region.ShouldBe("eu-west-1");
}