使用ASP.NET MVC实现字段验证的最佳方法是什么？

public class User
{
    [Required]
    public string Username { get; set; }

    [Required]
    public string Password { get; set; }
}

[HttpPost]
public ActionResult Login(User user)
{
    if (ModelState.IsValid)
    {
        // 验证通过，执行登录操作
    }
    else
    {
        // 验证失败，返回错误消息
        return View(user);
    }
}

@Html.ValidationMessageFor(model => model.Username)
@Html.ValidationMessageFor(model => model.Password)