How to use a controller in another assembly in ASP.NET Core 3.0?

Question

The default dotnet core 3 web api template assumes the controllers are in the same assembly as the Startup.cs

How to make it aware of the controllers in a different assembly?

I personally like having my solutions more layered and depending only on what it needs to depend

MyApp.Host --> MyApp.WebApi --> MyApp.Application --> MyApp.Domain

So in MyApp.Host I don't want any direct dependency to MVC framework (although I know that in Dotnet Core 3 this is already implicit). The controllers are in MyApp.WebApi

Answer 1

The solution is to .AddApplicationPart(assembly) when adding the controllers in Startup.cs.

So if I have a project MyApp.WebApi that has a dependency to the nuGet package: Microsoft.AspNetCore.Mvc.Core (current version is 2.2.5) with the following controller:

using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;

namespace MyApp.WebApi.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class SamplesController 
        : ControllerBase
    {
        [HttpGet]
        public IEnumerable<string> Get()
        {
            var samples =
                new List<string>
                {
                    "sample1", "sample2", "sample3"
                };

            return samples;
        }
    }
}

and I have my Startup.cs in MyApp.Host as:

using MyApp.WebApi.Controllers;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System.Reflection;

namespace MyApp.Cmd.Host
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        public void ConfigureServices(IServiceCollection services)
        {
            var sampleAssembly = Assembly.GetAssembly(typeof(SamplesController));
            services
                .AddControllers()
                .AddApplicationPart(sampleAssembly)
                .AddControllersAsServices();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

then the app will detect the controllers in different assembly and I'll be able to access: https://localhost:5001/samples