private String isValide() {
        String errormessage = "";
        if (_dialog.getFirstName().equals("")) {
            errormessage += "Vorname \n";
        }
        if (_dialog.getLastName().equals("")) {
            errormessage += "Nachname \n";
        }
        if (_dialog.getGender() == null) {
            errormessage += "Geschlecht \n";
        }


        if (!_dialog.getBirthdate().equals("")) {
            try {
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd");
                birthday = new Date(sdf.parse(_dialog.getBirthdate()).getTime());
            } catch (Exception e) {
                errormessage += "Geburtsdatum \n";
            }
        }
        if (_dialog.getStreet().equals("")) {
            errormessage += "Straße \n";
        }
        if (_dialog.getPostCode().equals("")) {
            errormessage += "PLZ \n";
        }
        if (_dialog.getCity().equals("")) {
            errormessage += "Stadt \n";
        }
        if (_dialog.getLand().equals("")) {
            errormessage += "Land \n";
        }
        return errormessage;
    }