1.Routes.cs

ʃ.Route(ʅ => ʅ / "Hello" * Pipeline.Action<FirstComponent>() / (
                    ʅ / "World" * Pipeline.Action<SecondComponent>()
                  | ʅ / "Foobar" * Pipeline.Action<ThirdComponent>()));

2.middleware.cs

public class FirstComponent
{
    private readonly Func<IDictionary<string, object>, Task> next;

    public FirstComponent(Func<IDictionary<string, object>, Task> next)
    {
        this.next = next;
    }

    public async Task Invoke(IDictionary<string, object> environment)
    {
        await environment.WriteResponse("before#1");
        await this.next(environment);
        await environment.WriteResponse("after#1");
    }
}

public class SecondComponent
{
    private readonly Func<IDictionary<string, object>, Task> next;

    public SecondComponent(Func<IDictionary<string, object>, Task> next)
    {
        this.next = next;
    }

    public async Task Invoke(IDictionary<string, object> environment)
    {
        await environment.WriteResponse("before#2");
        await this.next(environment);
        await environment.WriteResponse("after#2");
    }
}

3.tests.cs

public class When_building_a_pipeline_with_options_invoking_the_first : When_building_a_pipeline_with_options
{
    private Because of = () => responseMessage = client.GetAsync("http://localhost/Hello/World").Result;

    private It should_execute_the_final_function = () => responseMessage.Content.ReadAsStringAsync().Result.ShouldEqual("before#1before#2after#2after#1");

    private It should_return_200 = () => responseMessage.StatusCode.ShouldEqual(HttpStatusCode.OK);
}

public class When_building_a_pipeline_with_options_invoking_the_second : When_building_a_pipeline_with_options
{
    private Because of = () => responseMessage = client.GetAsync("http://localhost/Hello/Foobar").Result;

    private It should_execute_the_final_function = () => responseMessage.Content.ReadAsStringAsync().Result.ShouldEqual("before#1before#3after#3after#1");

    private It should_return_200 = () => responseMessage.StatusCode.ShouldEqual(HttpStatusCode.OK);
}