using Microsoft.AspNetCore.Http; public class HomeController : Controller { private readonly IHttpContextAccessor _httpContextAccessor; public HomeController(IHttpContextAccessor httpContextAccessor) { _httpContextAccessor = httpContextAccessor; } public IActionResult Index() { // Storing a value in the session _httpContextAccessor.HttpContext.Session.SetString("UserId", "123"); // Retrieving a value from the session var userId = _httpContextAccessor.HttpContext.Session.GetString("UserId"); return View(); } }The package library for ISession would be the Microsoft.AspNetCore.Http package.