Loading and registering API Controllers From Class Library in ASP.NET core

Question

I am using ASP.NET Core 1.0.1. I have the following

• A class library that uses "Microsoft.AspNetCore.Mvc": "1.0.1" in order to develop my controllers:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;

namespace CoreAPIsLibrary.Controllers
{

    [Route("api/[controller]")]
    public class ValuesContoller : Controller
    { 
        public string Get()
        {
            return "value";
        }

        // GET api/values/5
        [HttpGet("{id}")]
        public string Get(int id)
        {
            return "value";
        }

        // POST api/values
        [HttpPost]
        public void Post([FromBody]string value)
        {
        }

        // PUT api/values/5
        [HttpPut("{id}")]
        public void Put(int id, [FromBody]string value)
        {
        }
    }
}

This is my class libray's project.json:

{
  "version": "1.0.0-*",

  "dependencies": {
    "Microsoft.AspNetCore.Mvc": "1.0.1",
    "NETStandard.Library": "1.6.0"
  },

  "frameworks": {
    "netstandard1.6": {
      "imports": "dnxcore50"
    }
  }
}

• Asp.net core application (Web API Template) that will host my controllers and reference that class library. However, It never hits the break point in the controller. Here is my startup class in the web application:

  using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using System.Reflection;
using CoreAPIsLibrary.Controllers;

namespace APIsHost
{
    public class Startup
    {
        public Startup(IHostingEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
                .AddEnvironmentVariables();
            Configuration = builder.Build();
        }

        public IConfigurationRoot Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc()
              .AddApplicationPart(typeof(ValuesContoller).GetTypeInfo().Assembly).AddControllersAsServices();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            loggerFactory.AddConsole(Configuration.GetSection("Logging"));
            loggerFactory.AddDebug();

            app.UseMvc(routes =>
            {
                routes.MapRoute("default", "{controller}/{action}/{id}");
            });
            //app.UseMvc();
        }
    }
}

I also checked if the controller was injected:

So, what is missing?

Answer 1

Maybe you're doing something wrong. So, here are the steps to make this work.

• Create a new project: ASP.NET Core Web Application (.NET Core);
• Choose the Web API template;
• Run the project and access the "api/values" to make sure it's working;
• Add a new project to the solution named ClassLibrary: Class Library (.NET Core);
• Delete the Class1.cs and create a TestController.cs class;

• Add the MVC dependency in the project.json from the ClassLibrary project:

  "dependencies": {
    "NETStandard.Library": "1.6.0",
    "Microsoft.AspNetCore.Mvc": "1.0.0"
  },
  

• Update your TestController.cs to be like this:

  [Route("api/[controller]")]
  public class TestController : Controller{
    [HttpGet]
    public IEnumerable<string> Get() {
      return new string[] { "test1", "test2" };
    }
  }
  

• Add the reference to ClassLibrary in your WebAPI Project: right-click on "References"->"Add Reference..." or update your project.json like this:

  "dependencies": {
    "Microsoft.NETCore.App": {
      "version": "1.0.0",
      "type": "platform"
    },
    "Microsoft.AspNetCore.Mvc": "1.0.0",
    "Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.0",
    "Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
    "Microsoft.Extensions.Configuration.FileExtensions": "1.0.0",
    "Microsoft.Extensions.Configuration.Json": "1.0.0",
    "Microsoft.Extensions.Logging": "1.0.0",
    "Microsoft.Extensions.Logging.Console": "1.0.0",
    "Microsoft.Extensions.Logging.Debug": "1.0.0",
    "Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
    "ClassLibrary": "1.0.0-*"
  },
  

• Update your Startup.cs ConfigureServices method:

  public void ConfigureServices(IServiceCollection services) {
    services.AddMvc().AddApplicationPart(Assembly.Load(new AssemblyName("ClassLibrary")));
  }
  

• Run the project again and access "api/test";

Answer 2

you don't need to do anything special in Startup.cs of the main web app, it just needs to reference the class library.

The one trick is that for your controllers to be discovered your class library must directly reference MVC in its project.json file dependencies section:

"Microsoft.AspNetCore.Mvc": "1.0.*"

UPDATE: for MVC app I did not need anything special in my Startup but in one of my api apps I did need it maybe because using attribute routing.

services.AddMvc()
            .AddApplicationPart(Assembly.Load(new AssemblyName("CSharp.WebLib")))
            ;

where CSharp.WebLib is the name of my class library

Answer 3

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    ...

    services.AddMvc()
        .AddApplicationPart(typeof(Namespace.SubNamespace.ControllerName).Assembly);

    ...
}

Answer 4

@Fabricio Koch

How does it work on following code, if i publish Enabling Trimming option in dotnet 5.

public void ConfigureServices(IServiceCollection services) {
  services.AddMvc().AddApplicationPart(Assembly.Load(new AssemblyName("ClassLibrary")));
}