marechai/Marechai/Areas/Identity/Pages/Account/Manage/ShowRecoveryCodes.cshtml.cs

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace Marechai.Areas.Identity.Pages.Account.Manage
{
    public class ShowRecoveryCodesModel : PageModel
    {
        [TempData]
        public string[] RecoveryCodes { get; set; }

        [TempData]
        public string StatusMessage { get; set; }

        public IActionResult OnGet()
        {
            if(RecoveryCodes        == null ||
               RecoveryCodes.Length == 0)
            {
                return RedirectToPage("./TwoFactorAuthentication");
            }

            return Page();
        }
    }
}