Improve minimal api routing with grouping

[ziaulhasanhamim]

Background and Motivation

The new minimal approach in asp.net core 6 is good. I mean it's great. But I don't this will be useful in a real web application. Because this doesn't have an easy way to integrate route grouping. With route grouping, minimal actions can be separated into multiple files easily with the help of normal or static(since c# doesn't support modules like f#) classes without using MVC or Razor pages.

Proposed API

namespace Microsoft.AspNetCore.Builder;

+ public class RouteGroup : IApplicationBuilder, IEndpointRouteBuilder
+ {
+     // Needed members to implement those interfaces
+ }

public class MinimalActionEndpointRouteBuilderExtensions
{
+     public static void IncludeRouteGroup(this IEndpointRouteBuilder endpoints, string pattern, RouteGroup routeGroup);
}

Usage Examples

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

RouteGroup usersRoutes = new();
usersRoutes.MapGet("{id}", (int id) => GetUserById(id));

app.IncludeRouteGroup("/api/users/", usersRoutes);

You can separate these route actions to multiple files easily. RouteGroup would become more useful if in the future c# gets support for top-level functions(not just for Program.cs).

[davidfowl]

Very express like, I like it, but we're pretty much done with new features for .NET 6, we'll consider it for .NET 7.

[davidfowl]

I'm not sure we need to implement IApplicationBuilder. We'd need to think through this a little bit.

cc @khalidabuhakmeh since you implemented something similar.

[ziaulhasanhamim]

I'm not sure we need to implement IApplicationBuilder. We'd need to think through this a little bit.

Yes. IEndpointRouteBuilder will enable us to do almost all necessary things. So IApplicationBuilder is not really needed in RouteGroup. But IApplicationBuilder can be used a create middleware specific to that route group.

[davidfowl]

@ziaulhasanhamim right, we have something similar today with IApplicationBuilder.Map, but you don't get an IEndpointRouteBuilder. I could envision something like this:

app.MapGroup("/api/users", group =>
{
    group.UseCors(); // Does this make sense?

    group.MapGet("/", (UsersDbContext db) => db.ToListAsync());
    group.MapGet("/{id}", (int id, UsersDbContext db) => db.Users.Find(id)); 
});

[ziaulhasanhamim]

@davidfowl yes right you are. That doesn't make sense. So IEndpointRouteBuilder is enough for RouteGroup.

[ziaulhasanhamim]

But one overload can be made with a delegate parameter.

public class MinimalActionEndpointRouteBuilderExtensions
{
     public static void IncludeRouteGroup(this IEndpointRouteBuilder endpoints, string pattern, RouteGroup routeGroup);
     public static void IncludeRouteGroup(this IEndpointRouteBuilder endpoints, string pattern, RouteGroup routeGroup, Func<HttpContext, Func<Task>, Task> onMatch);
}

The onMatch will be executed whenever URL for the route group will match.

[davidfowl]

Do we really need onMatch? What's that for?

[ziaulhasanhamim]

I won't say we really need that. But there might be a situation where we may want to execute a common piece of code for a group route. Maybe some logging.

[davidfowl]

public class EndpointRouteBuilderExtensions
{
     public static void MapGroup(this IEndpointRouteBuilder endpoints, string pattern, Action<IApplicationBuilder> configureApp, Action<IEndpointRouteBuilder> configureRoutes);
     public static void MapGroup(this IEndpointRouteBuilder endpoints, string pattern, Action<IEndpointRouteBuilder> configureRoutes);
}

app.MapGroup("/api/users", static app => app.UseBuffering(), routes => routes.MapGet("/", (TodoDb db) => db.ToListAsync()));
app.MapGroup("/api/users", routes => routes.MapGet("/", (TodoDb db) => db.ToListAsync()));

[ziaulhasanhamim]

MapGroup needs us to give a delegate parameter that will configure the routes. I'm not really convinced with that. I would like if MapGroup returns an IEndpointRouteBuilder instance and we will configure routes on that instance or it will take a parameter of type RouteGroup and we will configure route on that RouteGroup.

public class EndpointRouteBuilderExtensions
{
     public static IEndpointRouteBuilder MapGroup(this IEndpointRouteBuilder endpoints, string pattern);
}

var group = app.MapGroup("/api/users");
group.MapGet("/", (TodoDb db) => db.ToListAsync());

or

public class EndpointRouteBuilderExtensions
{
     public static IEndpointRouteBuilder MapGroup(this IEndpointRouteBuilder endpoints, string pattern, RouteGroup group);
}

RouteGroup group = new();
group.MapGet("/", (TodoDb db) => db.ToListAsync());
app.MapGroup("/api/users", group);

[davidfowl]

I like the first one:

var group = app.MapGroup("/api/users");
group.MapGet("/", (TodoDb db) => db.ToListAsync());

Can you do things like apply conventions to entire groups? For example:

var group = app.MapGroup("/api/users");
group.RequireAuthentication();
group.MapGet("/", (TodoDb db) => db.ToListAsync());

[ziaulhasanhamim]

Yes, I think we should be able to do that,