写

//创建xml文档
public void WriteXml()
{
    //实例化一个XmlDocument对象
    XmlDocument xDoc = new XmlDocument();
    //创建一个声明xml文档所需要的语法的变量
    XmlDeclaration declaration = xDoc.CreateXmlDeclaration("1.0", "utf-8", "yes");
    //添加声明
    xDoc.AppendChild(declaration);

    //一个xml文档必须要有一个根元素，创建根节点students
    XmlElement elem = xDoc.CreateElement("students");
    //添加根节点
    xDoc.AppendChild(elem);


    //创建子节点
    XmlElement elem1 = xDoc.CreateElement("student");
    //添加节点
    elem.AppendChild(elem1);

    //给节点添加属性
    elem1.SetAttribute("name", "张三");
    elem1.SetAttribute("num", "14");

    //创建子节点的子节点
    XmlElement elem1_1 = xDoc.CreateElement("语文成绩");
    //添加节点
    elem1.AppendChild(elem1_1);
    //增加节点中的数据
    elem1_1.InnerText = "90";


    //保存
    xDoc.Save("students.xml");
}

读

public void WriteXml()
{
    //实例化一个XmlDocument对象
    XmlDocument xDoc = new XmlDocument();
    //加载xml文档
    xDoc.Load("students");
    
    //获取根节点students
    XmlNode node = xDoc.SelectSingleNode("students");
    //获取根节点集合
    XmlNodeList nodeList = node.ChildNodes;
    
    foreach(XmlNode node in nodeList)
    {
        string name = node.Name;
        Console.WriteLine(name);
        //类型转换
        XmlElement elem = (XmlElement)node;
        string name = elem.GetAttribute("name");
        string age = elem.GetAttribute("age");
        Console.WriteLine(name + ":" + age);

        XmlNodeList childList = node.ChildNodes;
        foreach(XmlNode xn in childList)
        {
            //类型转换
            XmlElement xe = (XmlElement)xn;
            string className = xe.Name;
            string score = xe.InnerText;
            Console.WriteLine(className + ":" + score);
        }
    }
    //生成或者修改xml文档的时候，末尾一定要写save方法
    xDoc.Save("students.xml");
}