What is the purpose of service configuration methods in C#?

For dependency registration in a Dependency Injection container. This allows the application infrastructure to manage the creation of service instances and inject them where needed.

Main goals:

• Lifecycle management: Defining the lifespan of a service instance (Singleton, Scoped, Transient).
• Decoupled architecture: Reducing coupling between components through the use of abstractions (interfaces).
• Testability: Easy replacement of service implementations for unit testing.
• Configurability: Ability to replace one implementation with another without changing client code.

Example of service registration in ASP.NET Core:

// Startup.cs or Program.cs in Minimal APIs
public void ConfigureServices(IServiceCollection services)
{
    // Registering a service with Singleton lifecycle
    services.AddSingleton<ISingletonService, SingletonService>();

    // Registering a service with Scoped lifecycle
    services.AddScoped<IScopedService, ScopedService>();

    // Registering a service with Transient lifecycle
    services.AddTransient<ITransientService, TransientService>();

    // Registering MVC and other standard services
    services.AddControllersWithViews();
}

Service lifecycles:

Lifecycle	Description	Instances per HTTP request
Singleton	One instance for the entire application lifetime.	One
Scoped	One instance per request (in the HTTP context).	One
Transient	A new instance is created for each service request.	Multiple (per injection)