ASP.NET CORE 3.1 NULL exception error when reading session without initial value assignment

Question

HttpContext.Session.GetInt32 ("Id") throws null exception because session doesn't occur when my c# code is running first on my layaut page

Session ilk okunduğunda sanırım henüz oluşturulmamış olduğu için null exception fırlatıyor. hatta login sayfasında session girildikten sonra bile layout sayfasında okurken null exception fırlatıyor.

 public ActionResult Login(string sifre, string email)
        {
            var url = HttpContext.Session.GetString("url");

            User UserSrgu = (from p in db.User
                             where p.Email == email && p.Sifre == sifre
                             select p).SingleOrDefault();
            if (UserSrgu == null)
            {
                TempData["sayfaMsj"] = "Lütfen E-mail ve Şifrenizi doğru giriniz!!!";
                return View();
            }
            if (UserSrgu.Onaylimi)
            {
                if (UserSrgu.ResimYol == null || UserSrgu.ResimYol == "")
                {
                    UserSrgu.ResimYol = "/Content/nullimgs/no-image_ex.png";
                }


                **HttpContext.Session.SetInt32("Id", UserSrgu.Id);
                HttpContext.Session.SetString("KAdi", UserSrgu.KAdi);
                HttpContext.Session.SetString("AdSoyad", UserSrgu.AdSoyad);
                HttpContext.Session.SetString("Email", UserSrgu.Email);
                HttpContext.Session.SetString("ResimYol", UserSrgu.ResimYol);**




                if (url != null)
                {
                    url = HttpContext.Session.GetString("url");
                }
                else
                {
                    url = "login";
                }
                return Redirect(url.ToString());
            }
            else
            {
                TempData["sayfaMsj"] = "Lütfen E-mail adresinize gelen linkten doğrulma yapınız!!!";
                return View();
            }
        }

layaout.cshtml page

@page
@using Microsoft.AspNetCore.Http
@using System.Text
@{

    var contentKAdi = "";
    var contentAdSoyad = "";
    var contentEmail = "";
    var contentResimYol = "";
    int contentId = 0;

    try
    {
        ***usr = HttpContext.Session.Get<User>("user");
        contentId = (int)HttpContext.Session.GetInt32("Id"); 
        contentKAdi = HttpContext.Session.GetString("KAdi");***
    }
    catch
    {
        contentKAdi = "";
        contentAdSoyad = "";
        contentEmail = "";
        contentResimYol = "";
        contentId = 0;
    }


}

startap.cs

    public void ConfigureServices(IServiceCollection services)
    {
        var connection = Configuration.GetConnectionString("xxZZDatabase");
        services.AddDbContext<xxZZContext>(option => option.UseSqlServer(connection));
        services.AddHttpClient();
        services.AddControllersWithViews();
        services.AddHttpContextAccessor();
        services.AddDistributedMemoryCache();
        services.AddSession(options =>
        {
            options.IdleTimeout = TimeSpan.FromMinutes(10);
            options.Cookie.HttpOnly = true;
            options.Cookie.IsEssential = true;
            options.Cookie.Name = ".Erol.Aktepe";
        });

        services.Configure<CookiePolicyOptions>(options =>
        {           
            options.CheckConsentNeeded = context => false;
            options.MinimumSameSitePolicy = SameSiteMode.None;
        });

        services.AddApplicationInsightsTelemetry(Configuration);

        services.AddDistributedRedisCache(options =>
        {
            options.InstanceName = "Oturum";
            options.Configuration = "127.0.0.1";
        });



        services.AddMvc(options => options.EnableEndpointRouting = false) 
            .SetCompatibilityVersion(CompatibilityVersion.Version_3_0);

    }



    [Obsolete]
    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
    {

        app.UseSession();
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();           
        }
        else
        {
            app.UseExceptionHandler("/Error");            
        }


        app.UseStaticFiles();


        app.UseRouting();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllerRoute(
                name: "default",
                pattern: "{controller=xxxZZZ}/{action=Index}/{id?}");
        });
        app.UseMvc();

    }

SessionExtensions.cs

public static class SessionExtensions
{
    public static byte[] Get(this ISession session, string key);
    public static int? GetInt32(this ISession session, string key);
    public static string GetString(this ISession session, string key);
    public static void SetInt32(this ISession session, string key, int value);
    public static void SetString(this ISession session, string key, string value);
}

ActionResult

.....

            if (HttpContext.Session.Get<User>("user") == default(User))
            {
                HttpContext.Session.Set<User>("user", UserSrgu);
                var usr = HttpContext.Session.Get<User>("user");
            }
            HttpContext.Session.SetInt32("Id", UserSrgu.Id);
            var id = HttpContext.Session.GetInt32("Id");

..... UserSrgu.Id = 1 and UserSrgu -> full and id = null and usr = null

I passed layout.cshtml page by passing data with TempData

Answer 1

1-In the ConfigureServices method please make sure you have set CheckConsentNeeded to false.

services.Configure<CookiePolicyOptions>(options =>
        {                
            options.CheckConsentNeeded = context => false;
            options.MinimumSameSitePolicy = SameSiteMode.None;
        });

2- A call to AddSession in ConfigureServices.

public void ConfigureServices(IServiceCollection services)
{
    services.AddDistributedMemoryCache();

    services.AddSession(options =>
    {
        // Set a short timeout for easy testing.
        options.IdleTimeout = TimeSpan.FromSeconds(10);
        options.Cookie.HttpOnly = true;
        // Make the session cookie essential
        options.Cookie.IsEssential = true;
    });

3- in Configure method in startup.cs you should have :

  app.UseSession();