求教xml怎么插入新节点，比如

求教xml怎么插入新节点，比如

XmlDocument xmlDoc1 = new XmlDocument();
xmlDoc1.Load("1.xml");
XmlNodeList nodeList = xmlDoc1.DocumentElement.SelectNodes("class/student");
for (int i = 0; i < nodeList.Count; i++) //对每个student元素操作
{
XmlElement eAge = xmlDoc1.CreateElement("age");
eAge.InnerText = "19";
nodeList[i].AppendChild(eAge); // 新节点添加在最后
}
xmlDoc1.Save("1.xml");
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如果要给张三这个student元素加age，
XmlNode node = xmlDoc1.DocumentElement.SelectSingleNode("class/student[name='张三']");
XmlElement eAge = xmlDoc1.CreateElement("age");
eAge.InnerText = "19";
node.AppendChild(eAge); // 新节点添加在最后