XmlDocument,XmlNode,XmlElement创建复杂XML文档

#region 生成XML消息
                    XmlDocument xmlDoc = new XmlDocument();


                    //生成描述版本
                    XmlDeclaration xmlDec;
                    xmlDec = xmlDoc.CreateXmlDeclaration("1.0", "gb2312", "yes");
                    xmlDoc.InsertBefore(xmlDec, xmlDoc.DocumentElement);

                    //定义根节点
                    XmlElement element;
                    XmlNode rootNode;
                    XmlNode subNode;
                    element = xmlDoc.CreateElement("message");
                    element.SetAttribute("System", "ATMS");
                    element.SetAttribute("Ver", "1.0");
                    rootNode = xmlDoc.AppendChild(element);

                    //定义子系统
                    element = xmlDoc.CreateElement("systemtype");
                    element.InnerText = SubType;
                    rootNode.AppendChild(element);

                    //定义消息类型
                    element = xmlDoc.CreateElement("messagetype");
                    element.InnerText = "ALARM";
                    rootNode.AppendChild(element);

                    //定义子系统
                    element = xmlDoc.CreateElement("systemtype");
                    element.InnerText = SubType;
                    rootNode.AppendChild(element);

                    //发出消息的源ip地址
                    element = xmlDoc.CreateElement("sourceIP");
                    element.InnerText = "";
                    rootNode.AppendChild(element);

                    //接收消息的目的ip地址
                    element = xmlDoc.CreateElement("sourceIP");
                    element.InnerText = "";
                    rootNode.AppendChild(element);

                    //用户名
                    element = xmlDoc.CreateElement("user");
                    element.InnerText = "";
                    rootNode.AppendChild(element);

                    //密码
                    element = xmlDoc.CreateElement("password");
                    element.InnerText = "";
                    rootNode.AppendChild(element);

                    element = xmlDoc.CreateElement("Alarm");
                    element.InnerText = "";
                    rootNode.AppendChild(element);

                    element = xmlDoc.CreateElement("type");
                    element.InnerText = "";
                    rootNode.LastChild.AppendChild(element);

                    element = xmlDoc.CreateElement("device");
                    element.InnerText = "";
                    subNode=rootNode.LastChild.AppendChild(element);

                    element = xmlDoc.CreateElement("id");
                    element.InnerText = "";
                    subNode.AppendChild(element);

                    element = xmlDoc.CreateElement("name");
                    element.InnerText = "";
                    subNode.AppendChild(element);

                    element = xmlDoc.CreateElement("location");
                    element.InnerText = "";
                    subNode.AppendChild(element);

                    element = xmlDoc.CreateElement("errortype");
                    element.InnerText = "";
                    subNode.AppendChild(element);

                    element = xmlDoc.CreateElement("occurtime");
                    element.InnerText = "";
                    subNode.AppendChild(element);

                    element = xmlDoc.CreateElement("releasetime");
                    element.InnerText = "";
                    subNode.AppendChild(element);

                    element = xmlDoc.CreateElement("desc");
                    element.InnerText = "";
                    subNode.AppendChild(element);

                    string x = xmlDoc.OuterXml;
                    #endregion