Startup.cs

using System;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Authentication.OpenIdConnect;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.IdentityModel.Protocols.OpenIdConnect;

namespace TokenStoreMultiService
{
    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.Configure<CookiePolicyOptions>(options =>
            {
                // This lambda determines whether user consent for non-essential cookies is needed for a given request.
                options.CheckConsentNeeded = context => true;
                options.MinimumSameSitePolicy = SameSiteMode.None;
            });

            services.AddAuthentication(sharedOptions =>
            {
                sharedOptions.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
                sharedOptions.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;
            })
            .AddOpenIdConnect(options => {
                var aadConfig = Configuration.GetSection("AzureAd");

                options.ClientId = aadConfig.GetValue<string>("ClientId");
                options.ClientSecret = aadConfig.GetValue<string>("ClientSecret");
                options.Authority = "https://login.microsoftonline.com/common/v2.0";

                options.TokenValidationParameters.ValidateIssuer = false; // disabled for multi-tenant since issuer could be any tenant
                options.ResponseType = OpenIdConnectResponseType.Code;
            })
            .AddCookie();

            // Add session state, backed by default in-memory cache
            services.AddDistributedMemoryCache();
            services.AddSession(sessionOptions => {
                sessionOptions.Cookie.IsEssential = true;
            });

            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
        }

        // 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("/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();
            app.UseAuthentication();
            app.UseCookiePolicy();
            app.UseSession();

            app.UseMvc();
        }
    }
}