MainController.cs

public ActionResult CheckLogin() {

     if (HttpContext.Request.Cookies["LoginCookie"] == null)
     {
         return RedirectToAction("Login", "Main");
     }
     else
     {
         return View();
     }

}

public IActionResult Login() {
  
  // .. if login is successful
  HttpContext.Response.Cookies.Append("LoginCookie", "LoginIsValid");

}

public IActionResult MainPage() {
  CheckLogin();
  
  return View();

}

public IActionResult Logout() {
 
   HttpContext.Response.Cookies.Delete("LoginCookie");

}

{Output}

Expected: As I enter MainPage, I should be redirected to the Login page.

Actual: As I enter MainPage, I get full access.