MarkAsInvalid
void MarkAsInvalid(bool invalid);
fNewNicknameField->MarkAsInvalid(failures.Contains("nickname"));
fNewPasswordField->MarkAsInvalid(failures.Contains("passwordClear"));
fRepeatPasswordField->MarkAsInvalid(failures.Contains("repeatPasswordClear"));
fEmailField->MarkAsInvalid(failures.Contains("email"));
fCaptchaResultField->MarkAsInvalid(failures.Contains("captchaResponse"));
MarkAsInvalid(!fAllowEmpty);
MarkAsInvalid(!success);
invalid->MarkAsInvalid(true);
fTextControl->MarkAsInvalid(true);
fTextControl->MarkAsInvalid(false);