Library ApiController custom route

Question

I want to place a REST [ApiController] with multiple actions and sub routes in a class library that I plan to reuse across projects. I would like to register the controller route via endpoint routing and specify the main route name in the appsettings.json of each project.

So in project1 I have

GET /someRoute/stuff/1
DELETE /someRoute/stuff/1
POST /someRoute/stuff/1/otherStuff

and in project2

GET /otherRoute/stuff/1
DELETE /otherRoute/stuff/1
POST /otherRoute/stuff/1/otherStuff

The problem is [ApiController] requires a [Route] attribute that takes a static string, so I cannot set the route from the app using the library. Alternatively I have tried to register each individual action via MapControllerRoute (maybe a stupid approach), but not sure how to proceed when I have multiple actions (get/delete/post) on the same route (eg: /otherName/stuff/1). I am using .NetCore3.

I've read the documentation but can't seem to figure this one out so any input is appreciated.

EDIT: I would also like to have different authorization requirements per project. For example in project1 the controller might be restricted to admins, in project2 it should satisfy a policy and finally let's say in project3 it should be open to everybody (no authorization required).

Answer 1

Really dirty way to do this, but I am not sure if you have shorter and better options.

Library project I am going to create custom attribute that would override RouteAttribute's template with value from config. Firstly, since we don't have a way to use dependency injection with attributes, we need static resolver, taken from here.

using System;

namespace ClassLibrary1
{
    public class AppDependencyResolver
    {
        private static AppDependencyResolver _resolver;

        public static AppDependencyResolver Current
        {
            get
            {
                if (_resolver == null)
                    throw new Exception("AppDependencyResolver not initialized. You should initialize it in Startup class");
                return _resolver;
            }
        }

        public static void Init(IServiceProvider services)
        {
            _resolver = new AppDependencyResolver(services);
        }

        private readonly IServiceProvider _serviceProvider;

        public object GetService(Type serviceType)
        {
            return _serviceProvider.GetService(serviceType);
        }

        public T GetService<T>()
        {
            return (T)_serviceProvider.GetService(typeof(T));
        }

        private AppDependencyResolver(IServiceProvider serviceProvider)
        {
            _serviceProvider = serviceProvider;
        }
    }
}

Next thing, custom attribute that inherits from RouteAttribute

using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;

namespace ClassLibrary1
{
    public class DynamicRouteAttribute : RouteAttribute
    {
        public DynamicRouteAttribute(string template) : base(ModifyTemplate(template))
        {
        }

        private static string ModifyTemplate(string template)
        {
            var config = AppDependencyResolver.Current.GetService<IConfiguration>();
            var routePrefix = config.GetValue<string>("route");

            return routePrefix + "/" + template;
        }
    }
}

And controller itself

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Routing;

namespace ClassLibrary1
{
    [DynamicRoute("stuff")]
    [ApiController]
    public class LibraryController : ControllerBase
    {
        [Route("")]
        [HttpGet]
        public void Get(int id)
        { }

        [Route("")]
        [HttpDelete]
        public void Delete(int id)
        { }

        [Route("")]
        [HttpPost]
        public void Post(int id)
        { }
    }
}

Parent (Web) project. Register your static resolver

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    AppDependencyResolver.Init(app.ApplicationServices);
    ...
}

And put your prefix value to appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*",
  "route": "someRoute"
}

Using this solution we can check all available routes. For the second web projects steps will be the same, just different value in config file.