XmlAttribute id = doc.CreateAttribute("id");
                id.Value = (i + 1).ToString();

                XmlAttribute type = doc.CreateAttribute("type");
                type.Value = comboBoxNO2.SelectedItem.ToString();

                XmlAttribute active = doc.CreateAttribute("active");
                active.Value = checkBoxNO2.Checked ? "true" : "false";

                newCondition.Attributes.Append(id);
                newCondition.Attributes.Append(type);
                newCondition.Attributes.Append(active);

                newCondition.InnerText = comboBoxNO2.SelectedItem.ToString() == "between" ? textBoxNO2.Text + "-" + textBoxNO2Max.Text : textBoxNO2.Text;

                parameter.AppendChild(newCondition);
                doc.Save("trigger-rules.xml");