BlazorEditForms/Model/User.cs

using System.ComponentModel.DataAnnotations;

using FluentValidation;
using FluentValidation.Validators;

namespace BlazorEditForms.Model;

public class User
{
    [Required]
    [EmailAddress]
    public string UserId { get; set; } = string.Empty;
    [Required]
    [MinLength(3)]
    public string Code { get; set; } = string.Empty;
}

public class UserValidator : AbstractValidator<User>
{
    public UserValidator()
    {
        RuleFor(u => u.UserId).NotEmpty().EmailAddress();
        RuleFor(x => x.Code).NotEmpty().MinimumLength(3);
    }
}