Setting up a component in ASP.Net 5

There are different ways to configure a component in ASP.Net 5:

• the AddXXX method used to add services,
• the ConfigureXXX method used to configure parameters,
• UseXXX method, use to register middleware in the pipeline.

The ConfigureXXX () method is responsible for configuring a component or subcomponent:

https://github.com/aspnet/Security/blob/dev/src/Microsoft.AspNet.Authorization/ServiceCollectionExtensions.cs#L12

public static IServiceCollection ConfigureAuthorization(
    [NotNull] this IServiceCollection services, 
    [NotNull] Action<AuthorizationOptions> configure)
{
    return services.Configure(configure);
}

      

        
        
        
      

    

https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNet.Mvc.Core/DependencyInjection/MvcCoreServiceCollectionExtensions.cs#L50

public static void ConfigureMvc(
    [NotNull] this IServiceCollection services,
    [NotNull] Action<MvcOptions> setupAction)
{
    services.Configure(setupAction);
}

      

        
        
        
      

    

But sometimes ConfigureXXX is a little more complicated: https://github.com/aspnet/Security/blob/dev/src/Microsoft.AspNet.Authentication.Cookies/CookieServiceCollectionExtensions.cs#L31

public static IServiceCollection ConfigureCookieAuthentication(
    [NotNull] this IServiceCollection services, 
    [NotNull] IConfiguration config, 
    string optionsName)
{
    return services.Configure<CookieAuthenticationOptions>(config, optionsName);
}

      

        
        
        
      

    

Why are some existing components more “customizable” than others?

As a component writer, what should I practice?

Another related question: Sometimes AddXXX and UseXXX let you customize a component: https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNet.Mvc.Core/DependencyInjection/MvcCoreServiceCollectionExtensions.cs#L32

public static IMvcBuilder AddMvcCore(
    [NotNull] this IServiceCollection services,
    [NotNull] Action<MvcOptions> setupAction)
{
    ConfigureDefaultServices(services);
    AddMvcCoreServices(services);
    services.Configure(setupAction);
    return new MvcBuilder() { Services = services, };
}

      

        
        
        
      

    

https://github.com/aspnet/Security/blob/dev/src/Microsoft.AspNet.Authentication.OAuth/OAuthAuthenticationExtensions.cs#L22

public static IApplicationBuilder UseOAuthAuthentication(
    [NotNull] this IApplicationBuilder app, 
    [NotNull] string authenticationScheme, 
    Action<OAuthAuthenticationOptions> configureOptions = null)
{
    return app.UseMiddleware<OAuthAuthenticationMiddleware<OAuthAuthenticationOptions>>(
    // [...]
}

      

        
        
        
      

    

Basically, what's the difference between setting parameters using three different methods? Especially when it's available on a single component.