How To Use Swagger With ASP.NET Core Web APIs

John Kocer
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If you are a developer, tester, or manager, sometimes understanding the various methods of API can be a challenge when building and consuming the application.

Generating good documentation and help pages for your Web API, using Swagger with .NET Core is as easy as adding a couple of NuGet and modifying the Startup.cs

Let’s start downloading simple To-do projects from Github.

Download and run TodoMvcSolution from the below link.
https://github.com/SmartITAz/TodoMvcSolution
NuGet Packages
Install the below NuGet package
Install-Package Swashbuckle.AspNetCore

Configure Swagger in the Startup.cs

Add the Swagger generator to the service collection after services.AddMvc();

Enable the middleware for serving the generated JSON document after the app.UseStaticFiles();

Add the below background yellow lines in your Startup file.

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Swashbuckle.AspNetCore.Swagger;

namespace Todo.Mvc.Ui
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration 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();

            // Register the Swagger generator, defining one or more Swagger documents
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new Info { Title = "My API", Version = "v1" });
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                app.UseBrowserLink();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
            }

            app.UseStaticFiles();

            // Enable middleware to serve generated Swagger as a JSON endpoint.
            app.UseSwagger();

            // Enable middleware to serve swagger-ui (HTML, JS, CSS, etc.), specifying the Swagger JSON endpoint.
            app.UseSwaggerUI(c =>
            {
                c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
            });


            app.UseMvc(routes =>
            {
                routes.MapRoute(
                              name: "default",
                              template: "{controller=Todo}/{action=Index}/{id?}");
            });
        }
    }
}

Go to http://localhost:63274/swagger/

Note. Your local port number may be different than ours, use your local port number.

Local port number

Click on Try it out and you will see the response in the Response body section.

ASP.NET Core

Here is the Web API

// Copyright 2017 (c) SmartIT. All rights reserved.
// By John Kocer
// This file is for Swagger test, this application does not use this file

using System.Collections.Generic;
using Microsoft.AspNetCore.Mvc;
using SmartIT.Employee.MockDB;

namespace TodoAngular.Ui.Controllers
{
    [Produces("application/json")]
    [Route("api/Todo")]
    public class TodoApiController : Controller
    {
        TodoRepository _todoRepository = new TodoRepository();

        [Route("~/api/GetAllTodos")]
        [HttpGet]
        public IEnumerable<SmartIT.Employee.MockDB.Todo> GetAllTodos()
        {
            return _todoRepository.GetAll();
        }

        [Route("~/api/AddTodo")]
        [HttpPost]
        public SmartIT.Employee.MockDB.Todo AddTodo([FromBody]SmartIT.Employee.MockDB.Todo item)
        {
            return _todoRepository.Add(item);
        }

        [Route("~/api/UpdateTodo")]
        [HttpPut]
        public SmartIT.Employee.MockDB.Todo UpdateTodo([FromBody]SmartIT.Employee.MockDB.Todo item)
        {
            return _todoRepository.Update(item);
        }

        [Route("~/api/DeleteTodo/{id}")]
        [HttpDelete]
        public void Delete(int id)
        {
            var findTodo = _todoRepository.FindById(id);
            if (findTodo != null)
                _todoRepository.Delete(findTodo);
        }
    }
}

Note. We have two controller files, TodoController and TodoApiController. TodoController is an MVC Controller and Swagger did not show the API methods, because it does not know how to route and also controller methods return a View.

public class TodoController : Controller
{
  TodoRepository _todoRepository = new TodoRepository();

  // GET: Todo
  public ActionResult Index()
  {
    var todos = (List<SmartIT.Employee.MockDB.Todo>)_todoRepository.GetAll();
    return View(todos);
  }

  // GET: Todo/Details/5
  public ActionResult Details(int id)
  {
    var findTodo = _todoRepository.FindById(id);
    return View(findTodo);
  }

  // GET: Todo/Create
  public ActionResult Create()
  {
    return View();
  }

  // POST: Todo/Create
  [HttpPost]
  [ValidateAntiForgeryToken]
  public ActionResult Create(IFormCollection collection)
  {
    try
    {
      _todoRepository.Add(new SmartIT.Employee.MockDB.Todo() { Name = collection["Name"] });

      return RedirectToAction(nameof(Index));
    }
    catch
    {
      return View();
    }
  }
}