tiku-backend.net/Tiku.Infrastructure/Auth/LetterAndDigitPasswordValidator.cs

using Microsoft.AspNetCore.Identity;

namespace Tiku.Infrastructure.Auth;

public sealed class LetterAndDigitPasswordValidator<TUser> : IPasswordValidator<TUser>
    where TUser : class
{
    public Task<IdentityResult> ValidateAsync(
        UserManager<TUser> manager,
        TUser user,
        string? password)
    {
        var valid = password is { Length: >= 8 } &&
                    password.Any(char.IsLetter) &&
                    password.Any(char.IsDigit);
        return Task.FromResult(valid
            ? IdentityResult.Success
            : IdentityResult.Failed(new IdentityError
            {
                Code = "PasswordRequiresLetterAndDigit",
                Description = "Password must be at least 8 characters and contain both letters and digits."
            }));
    }
}