The DOM model of C # XML parsing

The DOM works by first loading the XML document into memory one at a time, and then creating a "tree structure" in memory based on the elements and attributes defined in the document, which is a Document object model, meaning that the document is object-oriented, and each node in the document corresponds to an object in the model. And we all know that objects provide programming interfaces, so in application we use this set of objects to access XML documents and manipulate XML documents.

Illustrates the process of application and DOM interaction:

Dom creates a tree model in memory:

Fragment of XML document:

<parent>

<child id= "123" >text here</child>

</parent>

The tree structure in memory is as follows:

The main steps of C # to handle the DOM:

1. Declare the XmlDocument object and load the XML file or fragment;

Xmldocument doc=new Xmldocument (); Don't forget to import System.Xml

Doc.load ("Test.xml");//Load XML file

Doc.loadxml ("<book>abc</book>"); reprint XML Fragments

2. Declare the XmlElement variable object and assign it with doc.documentelement (the root element of the resulting XML file is not the root node)

XmlElement Root=doc. DocumentElement ();

3. Find the node and do the appropriate operation:

1) Find a single node: One method: Using the Get series method, such as Getfirstchild (), and the other method is selectSingleNode ("corresponding XPath string");

2) The lookup node set has two objects XmlNodeList and XmlNamedNodeMap, the former used more, the latter used to process the unordered node set processing XML fragments.

Method One

XmlNodeList El=n.childnodes; Get all child node sets of n

Method Two

XmlNodeList el=n.selectnodes ("book"); Gets the node set named book for the node

Method Three

XmlElement Rootele=doc. DocumentElement;

XmlNodeList el=rootele.getelementsbytagname ("book");

Method Four

XmlNodeList El=doc. getElementsByTagName ("book");

4. Create a new node main steps:

1) Use the XmlDocument object and populate it with XML

2) determine where to insert and navigate to this location

3) Create node (can also be: Element, Attribute, Text, Comment, CDATA, or processing &instruction)

4) Add the node to the Xmldocment object again

(Note: There are three ways to add a node.) AppendChild (), InsertBefore () and InsertAfter ();)

(i): Create ELEMENT nodes

XmlElement Elem=doc. CreateElement ("Price");

XmlElement (object). InnerText ();

XmlNode (object). createTextNode ();

(ii): setting Properties for ELEMENT nodes

SetAttribute () This method is a change, the non-invasive.

(iii): Create other types of nodes

Xmldocument.createcomment () method to annotate nodes

Xmldocument.createcdatasection ()

Xmldocument.createprocessinginstruction ()

5. Modifying and deleting nodes

ReplaceChild ();

SetAttribute ();

RemoveChild ();

RemoveAttribute ();

RemoveAll ();

6. Save the XML document

Xmldocument.save (XMLfileName);

Two important classes: XmlNode Class and XmlDocument class

The DOM model of C # XML parsing