private void ValidateRegistration()
{
//validation
if (string.IsNullOrEmpty(Name) || Name.Length > 100)
throw new InvalidUserRegistrationDataException("Name is invalid");
if (string.IsNullOrEmpty(Password) || Password.Length > 100)
throw new InvalidUserRegistrationDataException("Password is invalid");
if (string.IsNullOrEmpty(Huid) || Huid.Length > 1000)
throw new InvalidUserRegistrationDataException("Huid is invalid");
if (Age < 13 || Age > 1000)
throw new InvalidUserRegistrationDataException("Age is invalid");
if (string.IsNullOrEmpty(Country) || Country.Length > 100)
throw new InvalidUserRegistrationDataException("Contry is invalid");
UpdateLastOnline();
RegisteredAt = DateTime.UtcNow;
}