Add extensions for super simple HTTP service application building

[DamianEdwards]

Some people want to have as little code as possible in a single file (Program.cs) to stand up very simple HTTP services (no, I won't say "micro-services").

In other platforms (Go, Node, etc.) it's generally very easy to get an HTTP server up with some basic dispatching to various request-handling functions based on URL path. Doing this in ASP.NET Core today requires slightly more ceremony (Using IApplicationBuilder, RouteBuilder, a Startup class, etc.) but this can be very easily fixed with a couple of new extension methods in Routing.

Super simple HTTP service application:

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;

namespace NotAMicroService
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var host = new WebHostBuilder()
                .UseKestrel()
                .UseUrls("http://+:8080/") // optional, we default to listening on http://localhost:5000/
                .Configure(app => app
                    .UseRouter(router => router
                        .MapGet("hello/{*name}", (req, res, data) => res.WriteAsync($"Hello, {data.Values["name"]}!"))
                        .MapGet("goodbye/{*name}", (req, res, data) => res.WriteAsync($"Goodbye, {data.Values["name"]}!"))
                        .MapGet("{*name}", (req, res, data) => res.WriteAsync($"Welcome, {data.Values["name"]}!"))
                    )
                )
                .Build();

            host.Run();
        }
    }
}

Extension methods we need to add to Microsoft.AspNetCore.Routing to make this work:

using System;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.DependencyInjection;

namespace Microsoft.AspNetCore.Hosting
{
    public static class WebHostExtensions
    {
        public static IWebHostBuilder UseRouter(this IWebHostBuilder builder, Action<RouteBuilder> routeBuilder)
        {
            return builder
                .ConfigureServices(services => services.AddRouting())
                .Configure(app =>
                {
                    var router = new RouteBuilder(app);
                    routeBuilder(router);
                    app.UseRouter(router.Build());
                });
        }
    }
}

using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;

namespace Microsoft.AspNetCore.Hosting
{
    public static class RouteBuilderExtensions
    {
        public static IRouteBuilder MapGet(this IRouteBuilder builder, string template, Func<HttpRequest, HttpResponse, RouteData, Task> handler)
        {
            builder.MapGet(template, context =>
            {
                return handler(context.Request, context.Response, context.GetRouteData());
            });
            return builder;
        }
    }
}

[dustinmoris]

Hey, I saw this watching yesterday's standup today and think this is a brilliant idea. Can I suggest to add an overload which defines the handler as Func<HttpContext, RouteData, Task> or even just Func<HttpContext, Task> (probably the latter makes more sense)? Also just having the extension method names to be Get, Post, etc. reads much nicer than MapGet and then it already looks very much like other "micro" frameworks.

[DamianEdwards]

@dustinmoris yep agreed, would be nice to have that one too. Not sure about going all the way to just Get, Post, etc. methods. Of course, nothing stopping anybody from creating those extensions methods themselves 😄

[Eilon]

@kichalla can you work with folks on finalizing a design, and then implement?

[kichalla]

cc @rynowak

[rynowak]

@DamianEdwards - we already have a bunch of extensions with similar flavour on IRouteBuilder. Hopefully what's there is a good match for what you had in mind or else it's going to get confusing.

https://github.com/aspnet/Routing/blob/dev/src/Microsoft.AspNetCore.Routing/RequestDelegateRouteBuilderExtensions.cs