C# Notes

XML

1 - XmlDocument - W3C, DOM Level 2, Read-Write

namespace: System.Xml

associated types: XmlNode, XmlAttribute, XmlAttributeCollection

load from file: Load (Stream) , Load (URL), LoadXml (String)

search / iterate:

SelectNodes ( xpath string ), SelectSingleNode ( xpath string )

XmlNode.Name, Attributes, FirstChild, ChildNodes, Item: ["name"] , NextSibling

2 - XPATH Search ( W3Schools: http://www.w3schools.com/Xpath/default.asp )

Selecting Nodes

Expression Description
nodename Selects all child nodes of the named node
/ Selects from the root node
// Selects nodes in the document from the current node that match the selection no matter where they are
. Selects the current node
.. Selects the parent of the current node
@ Selects attributes

Examples

Path Expression Result
bookstore Selects all the child nodes of the bookstore element
/bookstore Selects the root element bookstore

Note: If the path starts with a slash ( / ) it always represents an absolute path to an element!

bookstore/book Selects all book elements that are children of bookstore
//book Selects all book elements no matter where they are in the document
bookstore//book Selects all book elements that are descendant of the bookstore element, no matter where they are under the bookstore element
//@lang Selects all attributes that are named lang

Path Expression Result
/bookstore/book[1] Selects the first book element that is the child of the bookstore element.

Note: IE5 and later has implemented that [0] should be the first node, but according to the W3C standard it should have been [1]!!

/bookstore/book[last()] Selects the last book element that is the child of the bookstore element
/bookstore/book[last()-1] Selects the last but one book element that is the child of the bookstore element
/bookstore/book[position()<3] Selects the first two book elements that are children of the bookstore element
//title[@lang] Selects all the title elements that have an attribute named lang
//title[@lang='eng'] Selects all the title elements that have an attribute named lang with a value of 'eng'
/bookstore/book[price>35.00] Selects all the book elements of the bookstore element that have a price element with a value greater than 35.00
/bookstore/book[price>35.00]/title Selects all the title elements of the book elements of the bookstore element that have a price element with a value greater than 35.00

Selecting Unknown Nodes

XPath wildcards can be used to select unknown XML elements.

Wildcard Description
* Matches any element node
@* Matches any attribute node
node() Matches any node of any kind

Examples

Path Expression Result
/bookstore/* Selects all the child nodes of the bookstore element
//* Selects all elements in the document
//title[@*] Selects all title elements which have any attribute

XPath Operators

Operator Description Example Return value
| Computes two node-sets //book | //cd Returns a node-set with all book and cd elements
+ Addition 6 + 4 10
- Subtraction 6 - 4 2
* Multiplication

6 * 4

24
div Division 8 div 4 2
= Equal price=9.80 true if price is 9.80
false if price is 9.90
!= Not equal price!=9.80 true if price is 9.90
false if price is 9.80
< Less than price<9.80 true if price is 9.00
false if price is 9.80
<= Less than or equal to price<=9.80 true if price is 9.00
false if price is 9.90
> Greater than price>9.80 true if price is 9.90
false if price is 9.80
>= Greater than or equal to price>=9.80 true if price is 9.90
false if price is 9.70
or or price=9.80 or price=9.70 true if price is 9.80
false if price is 9.50
and and price>9.00 and price<9.90 true if price is 9.80
false if price is 8.50
mod Modulus (division remainder) 5 mod 2 1

"//EXAMPLE/CUSTOMER[@id='2' or @type='C']"
"//EXAMPLE/CUSTOMER[@id='2' and @type='B']"
"//EXAMPLE/CUSTOMER[@id='1' and (@type='B' or @type='C')]"
"//EXAMPLE/CUSTOMER[contains(@type,'DECEA')]"

3 - XPathNavigator - Read-only

 

4 - XDocument - supports LINQ, Read-Write

namespace: System.Xml.Linq

associated types: XName, XElement

load from file: Load ("filename" )

search / iterate:

XElement : Attribute("name"), Attributes( ["name"] ), Element, Elements( ["name"] ),