services.AddSingleton<IXmlRepository, DataProtectionKeyService>();
services.AddSingleton<IConfigureOptions<KeyManagementOptions>>(serviceProvider =>
{
return new ConfigureOptions<KeyManagementOptions>(options =>
{
var scopeFactory = serviceProvider.GetRequiredService<IServiceScopeFactory>();
using (var scope = scopeFactory.CreateScope())
{
options.XmlRepository = scope.ServiceProvider.GetService<IXmlRepository>();
}
});
});

services.Configure<KeyManagementOptions>(options => options.XmlRepository = new DataProtectionKeyService(services.BuildServiceProvider()));

services.AddScoped<IXmlRepository, DataProtectionKeyService>()

services.AddSingleton<IXmlRepository, DataProtectionKeyService>()

JetBrains.Annotations

using JetBrains.Annotations;  


[assembly: AspMvcViewLocationFormat("~/Features/{1}/{0}.cshtml")]
[assembly: AspMvcViewLocationFormat("~/Features/Shared/{0}.cshtml")]
[assembly: AspMvcPartialViewLocationFormat("~/Features/{1}/{0}.cshtml")]
[assembly: AspMvcPartialViewLocationFormat("~/Features/Shared/{0}.cshtml")]

[assembly: AspMvcAreaViewLocationFormat("~/Areas/{2}/Features/{1}/{0}.cshtml")]
[assembly: AspMvcAreaViewLocationFormat("~/Areas/{2}/Features/Shared/{0}.cshtml")]
[assembly: AspMvcAreaViewLocationFormat("~/Features/Shared/{0}.cshtml")]
[assembly: AspMvcAreaPartialViewLocationFormat("~/Areas/{2}/Features/{1}/{0}.cshtml")]
[assembly: AspMvcAreaPartialViewLocationFormat("~/Areas/{2}/Features/Shared/{0}.cshtml")]
[assembly: AspMvcAreaPartialViewLocationFormat("~/Features/Shared/{0}.cshtml")]

class CustomerConfiguration : IEntityTypeConfiguration<Customer>
{
  public void Configure(EntityTypeBuilder<Customer> builder)
  {
     builder.HasKey(c => c.AlternateKey);
     builder.Property(c => c.Name).HasMaxLength(200);
   }
}

...
// OnModelCreating
builder.ApplyConfiguration(new CustomerConfiguration());

public Startup(IHostingEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
                .AddEnvironmentVariables();
            Configuration = builder.Build();
        }

public IConfiguration Configuration { get; }

public Startup(IConfiguration configuration)
{
     Configuration = configuration;
}

public static void Main(string[] args)
        {
            BuildWebHost(args).Run();
        }

        public static IWebHost BuildWebHost(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .Build();

public static IWebHost BuildWebHost(string[] args)
{
  return WebHost.CreateDefaultBuilder()
    .ConfigureAppConfiguration((ctx, cfg) =>
    {
      cfg.SetBasePath(Directory.GetCurrentDirectory())
        .AddJsonFile("config.json", true) // require the json file!
        .AddEnvironmentVariables();
    })
    .ConfigureLogging((ctx, logging) => { }) // No logging
    .UseStartup<Startup>()
    .Build();
}