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

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

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

        public RegisterConfirmationModel(UserManager<ApplicationUser> userManager, IEmailSender sender)
        {
            _userManager = userManager;
            _sender      = sender;
        }

        public string Email { get; set; }

        public bool DisplayConfirmAccountLink { get; set; }

        public string EmailConfirmationUrl { get; set; }

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

            ApplicationUser user = await _userManager.FindByEmailAsync(email);

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

            Email = email;

            // Once you add a real email sender, you should remove this code that lets you confirm the account
            DisplayConfirmAccountLink = true;

            if(DisplayConfirmAccountLink)
            {
                string userId = await _userManager.GetUserIdAsync(user);
                string code   = await _userManager.GenerateEmailConfirmationTokenAsync(user);
                code = WebEncoders.Base64UrlEncode(Encoding.UTF8.GetBytes(code));

                EmailConfirmationUrl = Url.Page("/Account/ConfirmEmail", null, new
                {
                    area = "Identity", userId, code, returnUrl
                }, Request.Scheme);
            }

            return Page();
        }
    }
}