public void doGet (HttpServletRequest req, HttpServletResponse res)
    throws ServletException, IOException {
  HttpSession sess = req.getSession (true);
}

using System;  
using System.Collections.Generic;  
using System.Diagnostics;  
using System.Linq;  
using System.Threading.Tasks;  
using Microsoft.AspNetCore.Http;  
using Microsoft.AspNetCore.Mvc;  
using Session_State.Models;  
  
namespace Session_State.Controllers  
{  
    public class HomeController : Controller  
    {  
  
        const string SessionName = "_Name";  
        const string SessionAge = "_Age";  
        public IActionResult Index()  
        {  
            HttpContext.Session.SetString(SessionName, "Jarvik");  
            HttpContext.Session.SetInt32(SessionAge, 24);  
            return View();  
        }  
  
        public IActionResult About()  
        {  
            ViewBag.Name = HttpContext.Session.GetString(SessionName);  
            ViewBag.Age = HttpContext.Session.GetInt32(SessionAge);  
            ViewData["Message"] = "Asp.Net Core !!!.";  
  
            return View();  
        }  
  
        public IActionResult Contact()  
        {  
            ViewData["Message"] = "Your contact page.";  
  
            return View();  
        }  
  
        public IActionResult Error()  
        {  
            return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });  
        }  
    }  
}