Startup.cs

using AlexaSkill.Data;
using AlexaSkill.Models;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Identity;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using System.Text.Encodings.Web;
using System.Threading.Tasks;

namespace SmartHomeApplet
{
    public class Startup
    {
        public IConfiguration Configuration { get; set; }

        public Startup(IHostingEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: true);

            if (env.IsDevelopment())
            {
                builder.AddUserSecrets<Startup>();
            }

            builder.AddEnvironmentVariables();
            builder.AddEnvironmentVariables("APPSETTING_");
            Configuration = builder.Build();
        }

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

            services.AddDbContext<ApplicationDbContext>(options =>
                options.UseSqlServer(Configuration["sql:connectionstring"]));

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

            services.AddAuthentication(o =>
            {
                o.DefaultAuthenticateScheme = CookieAuthenticationDefaults.AuthenticationScheme;
                o.DefaultSignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;
                o.DefaultChallengeScheme = CookieAuthenticationDefaults.AuthenticationScheme;
            })
                .AddCookieAuthentication(o => o.LoginPath = new PathString("/Account/Login"))
                .AddFacebookAuthentication(o =>
                {
                    o.AppId = Configuration["facebook:appid"];
                    o.AppSecret = Configuration["facebook:appsecret"];
                    o.SaveTokens = true;
                    o.Scope.Add("email");
                    o.Fields.Add("name");
                    o.Fields.Add("email");
                    o.Events.OnRemoteFailure = context =>
                    {
                        context.Response.Redirect($"/Account/ExternalError?error={UrlEncoder.Default.Encode(context.Failure.Message)}");
                        context.HandleResponse();
                        return Task.FromResult(0);
                    };
                });
        }

        // 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.UseAuthentication();

            app.UseStaticFiles();

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