How to Validate Security Stamp in Asp.Net Core 2

Hi guys,

I've been on this for days now trying to figure out how to validate security stamp inAsp.Net Core 2 to automatically signout user from previous logins. Below is my ConfigureServices and Login Method. Thanks in advance.

services.AddIdentity<GPayUsers, IdentityRole>(option =>
{
  option.User.RequireUniqueEmail = false;
  option.Password.RequiredLength = PasswordRequiredLength;
  option.Password.RequireDigit = PasswordRequireDigit;
  option.Password.RequiredUniqueChars = PasswordRequiredUniqueChars;
  option.Password.RequireLowercase = PasswordRequireLowercase;
  option.Password.RequireNonAlphanumeric = PasswordRequireNonAlphanumeric;
  option.Password.RequireUppercase = PasswordRequireUppercase;
  option.Lockout.MaxFailedAccessAttempts = LoginMaxFailedAccessAttempts;
}).AddEntityFrameworkStores<GPayContext>().AddDefaultTokenProviders();

services.ConfigureApplicationCookie(option =>
{
  option.ExpireTimeSpan = TimeSpan.FromMinutes(CookiesExpireMinute);
  option.LoginPath = new PathString("/Login");
  option.LogoutPath = new PathString("/Logout");
  option.AccessDeniedPath = new PathString("/Login");
  //option.Cookie.SecurePolicy = CookieSecurePolicy.Always;
});

public async Task<IActionResult> Login(LoginViewModel model)
        {
            try
            {
                if (ModelState.IsValid)
                {
                    ApplicationSettings applicationSettings = context.ApplicationSettings.FirstOrDefault();
                    GPayUsers user = await userManager.FindByNameAsync(model.UserName.Trim());
                    if (user != null)
                    {
                        await userManager.UpdateSecurityStampAsync(user);
                        user.TwoFactorEnabled = applicationSettings.EnableTwoFactorAuthentication;
                        user.LockoutEnabled = true;
                        if (!string.IsNullOrWhiteSpace(user.Email)) user.EmailConfirmed = applicationSettings.EnableTwoFactorAuthentication;
                        if (!string.IsNullOrWhiteSpace(user.PhoneNumber)) user.PhoneNumberConfirmed = applicationSettings.EnableTwoFactorAuthentication;
                        if (string.Equals(user.Status.ToUpper(), Status.L.ToString())) user.LockoutEnd = DateTime.Now.AddMonths(1);
                        await userManager.UpdateAsync(user);

                        if (user.DatePasswordChanged.HasValue)
                        {
                            int dayDifference = context.DBDateTime().Subtract(user.DatePasswordChanged.Value).Days;
                            if (dayDifference >= applicationSettings.PasswordExpires)
                            {
                                await signInManager.SignOutAsync();
                                return RedirectToAction(nameof(UserController.ChangePassword), new { id = user.Id, userType = Status.E.ToString() });
                            }
                        }

                        var result = await signInManager.PasswordSignInAsync(user, model.Password, false, true);

                        if (result.Succeeded)
                        {
                            switch (user.Status.ToUpper())
                            {
                                case "N":
                                    await signInManager.SignOutAsync();
                                    return RedirectToAction(nameof(UserController.ChangePassword), new { id = user.Id, userType = Status.N.ToString() });
                                default:
                                    return RedirectToAction(nameof(HomeController.Dashboard), "Home");
                            }
                        }
                        else if (result.IsLockedOut)
                        {
                            user.Status = Status.L.ToString();
                            await userManager.UpdateAsync(user);
                            ModelState.AddModelError(string.Empty, "This account has been locked out, please contact your system administrator.");
                            return View(model);
                        }
                        else if (result.RequiresTwoFactor)
                        {
                            return RedirectToAction(nameof(UserController.LoginWithTwoFA));
                        }
                        else
                        {
                            ModelState.AddModelError(string.Empty, "Invalid login attempt.");
                            return View(model);
                        }
                    }
                    else
                    {
                        ModelState.AddModelError(string.Empty, "Invalid login attempt.");
                        return View(model);
                    }
                }
            }
            catch (Exception ex)
            {
                ModelState.AddModelError(string.Empty, ex.Message);
                return View(model);
            }
            return View(model);
        }