Startup.cs

using EmployeeManagement.Models;
using EmployeeManagement.Security;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc.Authorization;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace EmployeeManagement
{
    public class Startup
    {
        private readonly IConfiguration _config;

        public Startup(IConfiguration config)
        {
            _config = config;
        }
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc(options => {
                options.EnableEndpointRouting = false;
                AuthorizationPolicy policy = new AuthorizationPolicyBuilder().RequireAuthenticatedUser().Build();
                options.Filters.Add(new AuthorizeFilter(policy));
            }).AddRazorRuntimeCompilation();

            services.AddScoped<IEmployeeRepository, SQLEmployeeRepository>();

            services.AddDbContextPool<AppDBContext>(
                options => options.UseSqlServer(_config.GetConnectionString("EmployeeDBConnection")));

            services.AddIdentity<ApplicationUser, IdentityRole>(options => 
            {
                options.Password.RequiredLength = 10;
                options.Password.RequiredUniqueChars = 3;
                options.Password.RequireNonAlphanumeric = false;
                
                options.SignIn.RequireConfirmedEmail = true;

                options.Tokens.EmailConfirmationTokenProvider = "CustomEmailConfirmation";

                options.Lockout.MaxFailedAccessAttempts = 5;
                options.Lockout.DefaultLockoutTimeSpan = TimeSpan.FromMinutes(15);
                options.Lockout.AllowedForNewUsers = true;
            }).AddEntityFrameworkStores<AppDBContext>().
            AddDefaultTokenProviders()
            .AddTokenProvider<CustomEmailConfirmationTokenProvider<ApplicationUser>>("CustomEmailConfirmation");

            services.AddAuthorization(options =>
            {
                        options.AddPolicy("DeleteRolePolicy", policy => 
                            policy.RequireClaim("Delete Role"));
                        
                        options.AddPolicy("AdminRolePolicy", policy => 
                            policy.RequireRole("Admin"));

                options.AddPolicy("EditRolePolicy", policy =>
                    policy.AddRequirements(new ManageAdminRolesAndClaimsRequirement()));
            });

            services.AddSingleton<IAuthorizationHandler, CanEditOnlyOtherAdminRolesAndClaimsHandler>();
            services.AddSingleton<IAuthorizationHandler, SuperAdminHandler>();

            services.ConfigureApplicationCookie(options => 
            options.AccessDeniedPath = new PathString("/Administration/AccessDenied"));

            services.AddAuthentication().AddGoogle(options => 
            {
                options.ClientId = "810931955972-aus2pia7egqpc7av42phkvl8a9jp3s2c.apps.googleusercontent.com";
                options.ClientSecret = "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";
            }).AddFacebook(options => 
            {
                options.AppId = "464241608602526";
                options.AppSecret = "c2e9ed0d225dc60f3a82942e6edb9d0c";
            });

            services.Configure<DataProtectionTokenProviderOptions>
                (options => options.TokenLifespan = TimeSpan.FromHours(5));

            services.Configure<CustomEmailConfirmationTokenProviderOptions>
                (options => options.TokenLifespan = TimeSpan.FromDays(3));

            services.AddSingleton<DataProtectionPurposeStrings>();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Error");
                app.UseStatusCodePagesWithReExecute("/Error/{0}");
            }

            app.UseStaticFiles();
            //app.UseMvcWithDefaultRoute();
            app.UseAuthentication();

            //Conventional routing
            app.UseMvc(routes => {
                routes.MapRoute("defult", "{controller=Home}/{action=Index}/{id?}");
            });

            /*app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapGet("/", async context =>
                {
                    await context.Response.WriteAsync("Hello World!");
                });
            });
            */
        }
    }
}