AspNetCore.Docs/aspnetcore/includes/combine-di.md

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Consider the following `ConfigureServices` method, which registers services and configures options:

[!code-csharp[](~/fundamentals/configuration/index/samples/3.x/ConfigSample/Startup2.cs?name=snippet)]

Related groups of registrations can be moved to an extension method to register services. For example, the configuration services are added to the following class:

[!code-csharp[](~/fundamentals/configuration/index/samples/3.x/ConfigSample/Options/MyConfigServiceCollectionExtensions.cs)]

The remaining services are registered in a similar class. The following `ConfigureServices` method uses the new extension methods to register the services:

[!code-csharp[](~/fundamentals/configuration/index/samples/3.x/ConfigSample/Startup4.cs?name=snippet)]

**_Note:_** Each `services.Add{GROUP_NAME}` extension method adds and potentially configures services. For example, <xref:Microsoft.Extensions.DependencyInjection.MvcServiceCollectionExtensions.AddControllersWithViews%2A> adds the services MVC controllers with views require, and <xref:Microsoft.Extensions.DependencyInjection.MvcServiceCollectionExtensions.AddRazorPages%2A> adds the services Razor Pages requires. We recommended that apps follow this naming convention. Place extension methods in the <xref:Microsoft.Extensions.DependencyInjection?displayProperty=fullName> namespace to encapsulate groups of service registrations.