Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using examples_dotnet_core.Data;
using examples_dotnet_core.Models;
using examples_dotnet_core.Services;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc.Formatters;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

namespace examples_dotnet_core
{
    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.AddDbContextPool<ApplicationDbContext>(options =>
                options.UseSqlite(Configuration.GetConnectionString("DefaultConnection"))
            );

            services.AddIdentity<ApplicationUser, IdentityRole>()
                .AddEntityFrameworkStores<ApplicationDbContext>()
                .AddDefaultTokenProviders();

            services.Configure<IdentityOptions>(options => {
                options.Password.RequireUppercase = false;
                options.Password.RequireLowercase = false;
                options.Password.RequiredLength = 6;
                options.Password.RequireNonAlphanumeric = false;
            });

            services.AddMvc(options => {
                options.RespectBrowserAcceptHeader = true;
                options.OutputFormatters.Add(new XmlSerializerOutputFormatter());
            });

            services.AddScoped<IEmailSender, EmailSender>();
            services.AddSingleton<IJokeProvider, ChuckNorrisJokeProvider>();
            
            
            /* services.AddSingleton<IJokeProvider>(
                serviceProvider => {
                    return new BufferedJokeProvider(new ChuckNorrisJokeProvider(), 3);
                }
            ); */
            /*
            services.AddTransient<IJokeProvider, ChuckNorrisJokeProvider>();
            services.AddScoped<IJokeProvider, ChuckNorrisJokeProvider>();  
             */
          
        }

        // 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();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
            }

            app.UseStaticFiles();

            app.UseAuthentication();

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