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

using System.ComponentModel.DataAnnotations;
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 ResetPasswordModel : PageModel
    {
        readonly UserManager<ApplicationUser> _userManager;

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

        [BindProperty]
        public InputModel Input { get; set; }

        public IActionResult OnGet(string code = null)
        {
            if(code == null)
            {
                return BadRequest("A code must be supplied for password reset.");
            }

            Input = new InputModel
            {
                Code = Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode(code))
            };

            return Page();
        }

        public async Task<IActionResult> OnPostAsync()
        {
            if(!ModelState.IsValid)
            {
                return Page();
            }

            ApplicationUser user = await _userManager.FindByEmailAsync(Input.Email);

            if(user == null)
            {
                // Don't reveal that the user does not exist
                return RedirectToPage("./ResetPasswordConfirmation");
            }

            IdentityResult result = await _userManager.ResetPasswordAsync(user, Input.Code, Input.Password);

            if(result.Succeeded)
            {
                return RedirectToPage("./ResetPasswordConfirmation");
            }

            foreach(IdentityError error in result.Errors)
            {
                ModelState.AddModelError(string.Empty, error.Description);
            }

            return Page();
        }

        public class InputModel
        {
            [Required, EmailAddress]
            public string Email { get; set; }

            [Required,
             StringLength(100, ErrorMessage = "The {0} must be at least {2} and at max {1} characters long.",
                          MinimumLength     = 6), DataType(DataType.Password)]
            public string Password { get; set; }

            [DataType(DataType.Password), Display(Name = "Confirm password"),
             Compare("Password", ErrorMessage          = "The password and confirmation password do not match.")]
            public string ConfirmPassword { get; set; }

            public string Code { get; set; }
        }
    }
}