Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using MVC_Company_Core.Domain;
using MVC_Company_Core.Domain.Repositories;
using MVC_Company_Core.Domain.Repositories.Abstract;
using MVC_Company_Core.Domain.Repositories.EntityFramework;
using MVC_Company_Core.Service;

namespace MVC_Company_Core
{
    public class Startup
    {
        public IConfiguration Configuration { get; }

        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public void ConfigureServices(IServiceCollection services)
        {
            Configuration.Bind("Project", new Config());

            services.AddTransient<ITextFieldsRepository, EFTextFieldsRepository>();
            services.AddTransient<IServiceItemsRepository, EFServiceItemsRepository>();
            services.AddTransient<DataManager>();

            services.AddDbContext<AppDbContext>(context => context.UseSqlServer(Config.ConnectionString));

            services.AddIdentity<IdentityUser, IdentityRole>(options =>
            {
                options.User.RequireUniqueEmail = true;
                options.Password.RequiredLength = 4;
                options.Password.RequireNonAlphanumeric = false;
                options.Password.RequireLowercase = false;
                options.Password.RequireUppercase = false;
                options.Password.RequireDigit = false;
            }).AddEntityFrameworkStores<AppDbContext>().AddDefaultTokenProviders();

            services.ConfigureApplicationCookie(options =>
            {
                options.Cookie.Name = "myCompanyAw";
                options.Cookie.HttpOnly = true;
                options.LoginPath = "/account/login";
                options.AccessDeniedPath = "/account/accessdenied";
                options.SlidingExpiration = true;
            });

            services.AddAuthorization(x =>
            {
                x.AddPolicy("AdminArea", policy => { policy.RequireRole("admin"); });
            });

            services.AddControllersWithViews(x =>
            {
                x.Conventions.Add(new AdminAreaAuthorization("Admin","AdminArea"));
            })
            .SetCompatibilityVersion(CompatibilityVersion.Version_3_0)
            .AddSessionStateTempDataProvider();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseStaticFiles();

            app.UseRouting();

            app.UseCookiePolicy();
            app.UseAuthentication();
            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute("admin", "{area:exists}/{controller=Home}/{action=Index}/{id?}");
                endpoints.MapControllerRoute("default", "{controller=Home}/{action=Index}/{id?}");
            });
        }
    }
}