marechai/Marechai/Areas/Identity/Pages/Account/ConfirmEmail.cshtml.cs

using System.Text;
using System.Threading.Tasks;
using Marechai.Database.Models;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.AspNetCore.WebUtilities;

namespace Marechai.Areas.Identity.Pages.Account
{
    [AllowAnonymous]
    public class ConfirmEmailModel : PageModel
    {
        readonly UserManager<ApplicationUser> _userManager;

        public ConfirmEmailModel(UserManager<ApplicationUser> userManager) => _userManager = userManager;

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

        public async Task<IActionResult> OnGetAsync(string userId, string code)
        {
            if(userId == null ||
               code   == null)
            {
                return RedirectToPage("/Index");
            }

            ApplicationUser user = await _userManager.FindByIdAsync(userId);

            if(user == null)
            {
                return NotFound($"Unable to load user with ID '{userId}'.");
            }

            code = Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode(code));
            IdentityResult result = await _userManager.ConfirmEmailAsync(user, code);
            StatusMessage = result.Succeeded ? "Thank you for confirming your email." : "Error confirming your email.";

            return Page();
        }
    }
}