C#操作Xml：使用XmlReader读Xml

2022-09-01 19:59:25

XmlDocument和XElement在读取Xml时要将整个Xml文档放到内存中去操作，这样做操作简单，但是很费内存和IO（可能是磁盘IO或者网络IO）；而在有些场景下我们必须考虑尽可能节省内存和IO的开销，这时候就该XmlReader和XmlWriter出场了。

XmlReader读取Xml需要通过Read()实例方法，不断读取Xml文档中的声明，节点开始，节点内容，节点结束，以及空白等等，直到文档结束，Read()方法返回false。

如下读取Xml内容实例代码和注释说明

//玉开技术博客：http://www.cnblogs.com/yukaizhao

using System;

using System.Collections.Generic;

using System.Text;

using System.Xml;

using System.IO;
 
namespace UseXmlReader
{

    class Program

    {

        static void Main(string[] args)

        {

            //声明StringReader传入Xml文本，作为XmlReader.Create的参数

            using (StringReader strRdr = new StringReader(@"<?xml version=""1.0"" encoding=""utf-8"" ?>
<root>

    <cat color=""white"">I‘m a Cat</cat>

    <dog color=""yellow""/>

</root>"))

            {

                //通过XmlReader.Create静态方法创建XmlReader实例

                using (XmlReader rdr = XmlReader.Create(strRdr))

                {

                    //循环Read方法直到文档结束

                    while (rdr.Read())

                    {

                        Console.WriteLine("rdr.NodeType = " + rdr.NodeType);

                        //如果是开始节点

                        if (rdr.NodeType == XmlNodeType.Element) {

                            //通过rdr.Name得到节点名

                            string elementName = rdr.Name;

                            Console.WriteLine(elementName + " element start");

                            if (elementName == "root") {
 
                            }

                            //读取到cat元素 这时rdr.Read()读取到的内容为<cat color="white">

                            else if (elementName == "cat")

                            {

                                //可以通过中括号获得属性值

                                string colorVal = rdr["color"];

                                Console.WriteLine("\tcat‘s color is " + colorVal);
 
                                //读取到节点内文本内容

                                if(rdr.Read()) {

                                    //通过rdr.Value获得文本内容

                                    Console.WriteLine("\t cat said:" + rdr.Value);

                                }

                            }

                        }

                        else if (rdr.NodeType == XmlNodeType.EndElement)

                        {

                            //在节点结束时也可以通过rdr.Name获得节点名字

                            string elementName = rdr.Name;

                            Console.WriteLine(elementName + " element end");

                        }

                    }

                }

            }
 
            Console.Read();

        }

    }
}