Introduction to XML I

Xml Basics 01

Concept ：

Extensible markup language , It is a way to store data in simple text format . Can be used for Serialization deserialization （ Serialization is done by converting objects into byte streams , To store or transfer objects to memory , The process of a database or file . The main purpose is to save the state of the object , Include the data of the object , So that the object can be rebuilt when needed . The reverse process is called Deserialization .）

xml The elements of - element：

A pair of angle brackets and angle bracket slashes together form a basic element . for example <> </>, Internally xml Label marking of . In the middle of the angle brackets is the content .

Such as : <book> Journey to the west </book>

​ <title> Journey to the west </title>

​ <auther> Wu chengen </auther>

Tags can have inclusive relationships , Nested relationships （ However, it is not recommended , The code is too complex to read ）

xml Elements and attributes of

attribute ： <book title=‘ Journey to the west ’>

​ </book>

The difference between elements and attributes ：

It is also the way of storing data

Not much difference

Elements cannot describe complex objects

xml Statement of

Declaration file format , edition , codec .

<?xml version="1.0"?><?xml version="1.0" encoding="utf-8" ?><?xml version="1.0" encoding="GBK" ?>

xml Notes

Annotation symbols

<!-- -->

xml Structure

Xml It provides a structured way to organize data , Unlike a relational database .

Xml Data is organized hierarchically , It's kind of similar windows explorer Folders and files in .

Every document must have a root element , It contains all elements and text data .（ That is, there must be a root tag element , Other tag elements are contained by it ）

<?xml version="1.0"?><books>	<book></book></books><!-- It's legal ->

xml The namespace of

That is to say xml Name a name .

For example, the following table :

<?xml version="1.0"?><books xmlns:myNS="123123">	<book></book></books>

xml The rules of

1. There must be a declaration statement

​ <? xml version=“1.0” ?>

2. Yes and only 1 A root element

3. Every element has a closed tag

4. There are no overlapping elements — All child elements must be completely nested within the parent element

5. All attributes must be enclosed in quotation marks

DTD Document definition type

It is not allowed to specify the data type of elements and attributes （ Yes xml The provisions of the document are binding ）

schema

frequently-used XSD XML Schema Deinition language

stay .net Also known as XML framework , You can specify the data structure of elements and attributes , With .xsd File storage

Namespace ：

http：//www.w3.org/2001/XMLSchema Root element ： <schema></schema>

<?xml version="1.0"encoding="utf-8"?><xs:schema id="SchemaBooks" targetNamespace="http://tempuri.org/SchemaBooks.xsd" elementFormDefault="qualified" xmins="http://tempuri.org/SchemaBooks.xsd" xmlns:mstns="http://tempuri.org/SchemaBooks.xsd" xmlns:xs="http://www.w3.org/2001/XMLSchema">	<xs:element name="Books">		<xs:complexType>			<xs:choice maxOccurs="unbounded">				<xs:element name="Book">					<xs:complexType>						<xs:sequence>							<xs:element name="title"type="xs:string"/>							<xs;element name="price"type="xs:decimal"/>						</xs;sequence>					</xs:complexType>				</xs:element>			</xs;choice>		</xs:complexType>	</xs:element></xs:schema><!--schema  Document root path （ Elements ）element  node choice  complex junction  maxOccurs  The number of nodes is limited unbounded  Is there a limit complexType  Specify the element type under this label ->

xml And xsd relation

stay vs in , Can pass

System.Data.DataSet ds = new System.Data.DataSet();ds.ReadXml("");ds.WriteXmlSchema("");// Can be xml The file is read and converted to xsd file 

xsd Several common defaults for ：

xmlns:xs=http://www.w3.org/2001/XMLSchema

schema The specification defines the namespaces of some basic data types

targetNamespace=http://tempuri.org/SchemaBookStore.xsd

The schema Of the namespace of URI quote .

xmlns=http://tempuri.org/SchemaBookStore.xsd

Ben XSD Namespace

xmlns:mstns=http://tempuri.org/SchemaBookStore.xsd

Ben XSD Namespace , The prefix name is mstns

Document object model

Document Object Model, DOM

Based on the object （ Based on trees ）（ Suitable for object extraction, etc ）

SAX

Simple API for XML

Based on flow 、 Push model （ Better performance , It is more suitable for reading and parsing data ）

DOM Document object model main classes

XmlNode: Express XML A single node in the document .

XmlDocument: Express XML file , Inherited from XmlNode .

XmlElement: Represents an element .

XmlAttribute Represents an attribute

XmlText: Represents the text content of the element .

XmlComment Express XML Content of notes .

XmlNodeList Represents a collection of nodes .

XmlNode.ChildNodes - Returns a that contains all children of the node XmlNodeList.

XmlNode.SelectNodes - Return contains matches XPath Of the node set queried XmlNodeList

XmlDocument Use

Definition ****XmlDocument

XmlDocument document = new XmlDocument();

load XMl file

document.Load(“XML file ”);

Namespace

using System.Xml;

Common properties ：

FirstChild Get the first child of the node . （ Inherited from XmlNode.）

DocumentElement Get the root of the document XmlElement.

Common methods

Load()

Save()

Get root node

document.FirstChild

Get the root element

document.DocumentElement

About XmlNode Several important attributes of

FirstChild

LastChild

HasChildNodes

ParentNode

NextSibling

Use DOM establish xml file

Create nodes ：

XmlDocument**** Method

CreateNode node

CreateElement Elements

CreateAttribute attribute

CreateTextNode Content

CreateComment notes

Insert node ：

XmlNode**** Method

AppendChild Final addition

InsertAfter Add before

InsertBefore Add

Delete node :

XmlNode Method

RemoveAll Delete all

RemoveChild Delete a

RemoveAttribute Delete a property