Detailed code examples for interpreting and writing XML files

This article will cover 3 aspects:
1. Accessing XML files
2. XML Document Object Model
3. XML and DataSet

Here we first introduce two objects for operating XML files: XmlTextReader and XmlTextWriter
The object used to open and read Xml files is the XmlTextReader object. The following example opens a sample file sample.xml

XmlTextReader reader = new XmlTextReader("sample.xml");

in the same path as the program. Then we can automatically facilitate the XML file through its Read method. Example:

while(reader.Read())
{
       //在这里填写对于XML的操作代码
}

Let’s look at a more complicated example.

while(reader.Read())
 2{
 3    switch(reader.NodeType)
 4    {
 5        case XmlNodeType.Element:   //当前节点是一个元素
 6              Console.Write("<" + reader.Name);
 7            while(reader.MoveToNextAttribute()) //按照顺序读取下一个属性
 8              Console.Write(" " + reader.Name + "=&#39;" + reader.Value + "&#39;");
 9            Console.Write(">");
10            break;
11        case XmlNodeType.DocumentType:  //XML文件的类型声明
12              Console.WriteLine(reader.NodeType + "<" + reader.Name + ">" + reader.Value);
13            break;
14        ……
15        }
16    }

Starting from line 3, we judge the type of node based on the NodeType attribute, and perform different processing according to different types of nodes.

The following table lists some commonly used node types.

## An attributeCDATAEscape text that would be treated as a markup language (such as HTML)Comment##Comments separated by DocumentDocumentType##ElementEndTagNone

##XmlTextReaderThe value of NodeType

Type

Description

All

All nodes

Attribute

The root node of the XML data tree

The type declaration of the document, that is, > tag

An element, usually the actual data in the XML file

The end position of the element

## is not a node

Text

Returns the text content of the element

XMLDeclaration

XML declaration node, for example

        在进行写入XML文件时我们使用的XmlTextWriter类，它是XmlWriter的子类，速度快且不使用缓存，但是同XmlTextReader一样，在写入XML文件时只能向前。

        我们假定要写入的XML文件在C盘根目录下：

XmlTextWriter writer = new XmlTextWriter("C:\\sample2.xml",null);

        在这里如果不想把数据写入文件，而只是想在命令窗口显示，则可以把“Console.Out”作为参数传递给构造器，此时应把上述语句改为：

XmlTextWriter writer = new XmlTextWriter(Console.Out);

        下面我们介绍一下写入XML文件数据的一些常用方法：

XmlTextWriter的常用方法
方法	说明	用法
WriteStartDocument	写XML声明部分，即“”	writer.WriteStartDocument();
WriteEndDocument	使没有闭合元素闭合	writer.WriteEndDocument();
WriteDocType	写DOCTYPE声明	writer.WriteDocType("sample2",null,null,"");
WriteStartElement	写元素的开始标志	writer.WriteStartElement("sample2");
WriteEndElement	写元素的结束标志	writer.WriteEndElement();
WriteString	写入字符串	writer.WriteString("Pride And Prejudice");
WriteCData	写CDATA块，即写入的文字在间	writer.WriteCData("Price 15% off!!");
WriteRaw	手工写入一行，不作任何处理	writer.WriteRaw("this & that");
WriteEntityRef	写入实体引用，即前面加“&”后面加“;”	writer.WriteEntityRef("h");
WriteProcessingInstruction	写入处理指令，即前面加“”后面加“?>”	writer.WriteProcessingInstruction("xml-stylesheet",PItext);
WriteComment	写入注释，自动加入注释标志“

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