XPath 入门
1. book.xml
book.xml
<?
xml version="1.0"
?>
<
catalog
>
<
book
id
="bk101"
>
<
author
>
Gambardella, Matthew
</
author
>
<
title
>
XML Developer's Guide
</
title
>
<
genre
>
Computer
</
genre
>
<
price
>
44.95
</
price
>
<
publish_date
>
2000-10-01
</
publish_date
>
<
description
>
An in-depth look at creating applications
with XML.
</
description
>
</
book
>
<
book
id
="bk102"
>
<
author
>
Ralls, Kim
</
author
>
<
title
>
Midnight Rain
</
title
>
<
genre
>
Fantasy
</
genre
>
<
price
>
5.95
</
price
>
<
publish_date
>
2000-12-16
</
publish_date
>
<
description
>
A former architect battles corporate zombies,
an evil sorceress, and her own childhood to become queen
of the world.
</
description
>
</
book
>
<
book
id
="bk103"
>
<
author
>
Corets, Eva
</
author
>
<
title
>
Maeve Ascendant
</
title
>
<
genre
>
Fantasy
</
genre
>
<
price
>
5.95
</
price
>
<
publish_date
>
2000-11-17
</
publish_date
>
<
description
>
After the collapse of a nanotechnology
society in England, the young survivors lay the
foundation for a new society.
</
description
>
</
book
>
<
book
id
="bk104"
>
<
author
>
Corets, Eva
</
author
>
<
title
>
Oberon's Legacy
</
title
>
<
genre
>
Fantasy
</
genre
>
<
price
>
5.95
</
price
>
<
publish_date
>
2001-03-10
</
publish_date
>
<
description
>
In post-apocalypse England, the mysterious
agent known only as Oberon helps to create a new life
for the inhabitants of London. Sequel to Maeve
Ascendant.
</
description
>
</
book
>
<
book
id
="bk105"
>
<
author
>
Corets, Eva
</
author
>
<
title
>
The Sundered Grail
</
title
>
<
genre
>
Fantasy
</
genre
>
<
price
>
5.95
</
price
>
<
publish_date
>
2001-09-10
</
publish_date
>
<
description
>
The two daughters of Maeve, half-sisters,
battle one another for control of England. Sequel to
Oberon's Legacy.
</
description
>
</
book
>
<
book
id
="bk106"
>
<
author
>
Randall, Cynthia
</
author
>
<
title
>
Lover Birds
</
title
>
<
genre
>
Romance
</
genre
>
<
price
>
4.95
</
price
>
<
publish_date
>
2000-09-02
</
publish_date
>
<
description
>
When Carla meets Paul at an ornithology
conference, tempers fly as feathers get ruffled.
</
description
>
</
book
>
<
book
id
="bk107"
>
<
author
>
Thurman, Paula
</
author
>
<
title
>
Splish Splash
</
title
>
<
genre
>
Romance
</
genre
>
<
price
>
4.95
</
price
>
<
publish_date
>
2000-11-02
</
publish_date
>
<
description
>
A deep sea diver finds true love twenty
thousand leagues beneath the sea.
</
description
>
</
book
>
<
book
id
="bk108"
>
<
author
>
Knorr, Stefan
</
author
>
<
title
>
Creepy Crawlies
</
title
>
<
genre
>
Horror
</
genre
>
<
price
>
4.95
</
price
>
<
publish_date
>
2000-12-06
</
publish_date
>
<
description
>
An anthology of horror stories about roaches,
centipedes, scorpions and other insects.
</
description
>
</
book
>
<
book
id
="bk109"
>
<
author
>
Kress, Peter
</
author
>
<
title
>
Paradox Lost
</
title
>
<
genre
>
Science Fiction
</
genre
>
<
price
>
6.95
</
price
>
<
publish_date
>
2000-11-02
</
publish_date
>
<
description
>
After an inadvertant trip through a Heisenberg
Uncertainty Device, James Salway discovers the problems
of being quantum.
</
description
>
</
book
>
<
book
id
="bk110"
>
<
author
>
O'Brien, Tim
</
author
>
<
title
>
Microsoft .NET: The Programming Bible
</
title
>
<
genre
>
Computer
</
genre
>
<
price
>
36.95
</
price
>
<
publish_date
>
2000-12-09
</
publish_date
>
<
description
>
Microsoft's .NET initiative is explored in
detail in this deep programmer's reference.
</
description
>
</
book
>
<
book
id
="bk111"
>
<
author
>
O'Brien, Tim
</
author
>
<
title
>
MSXML3: A Comprehensive Guide
</
title
>
<
genre
>
Computer
</
genre
>
<
price
>
36.95
</
price
>
<
publish_date
>
2000-12-01
</
publish_date
>
<
description
>
The Microsoft MSXML3 parser is covered in
detail, with attention to XML DOM interfaces, XSLT processing,
SAX and more.
</
description
>
</
book
>
<
book
id
="bk112"
>
<
author
>
Galos, Mike
</
author
>
<
title
>
Visual Studio 7: A Comprehensive Guide
</
title
>
<
genre
>
Computer
</
genre
>
<
price
>
49.95
</
price
>
<
publish_date
>
2001-04-16
</
publish_date
>
<
description
>
Microsoft Visual Studio 7 is explored in depth,
looking at how Visual Basic, Visual C++, C#, and ASP+ are
integrated into a comprehensive development
environment.
</
description
>
</
book
>
</
catalog
>
2. 新建一个类,包括两个主要的成员：Document
class
XPathSample
{
XPathDocument Document;
XPathNavigator Navigator;
};
3.使用构造函数进行初始化
public XPathSample()
{
Document = new XPathDocument("books.xml");
Navigator = Document.CreateNavigator();
}
4. 遍历所有的节点，输出xml中所有的数据
void NavigateDocument()
{
Navigator.MoveToRoot();
Navigator.MoveToFirstChild();
if(Navigator.NodeType == XPathNodeType.Element)
{
if(Navigator.HasChildren == true)
{
Navigator.MoveToFirstChild();
do
{
if(Navigator.HasAttributes == true)
{
Console.WriteLine("Book ID: " + Navigator.GetAttribute("id", ""));
}
if(Navigator.HasChildren)
{
Navigator.MoveToFirstChild();
do
{
Console.Write("\t{0}:\t{1}\r\n", Navigator.Name, Navigator.Value);
} while(Navigator.MoveToNext());
Navigator.MoveToParent();
}
} while(Navigator.MoveToNext());
}
}
}
5. 用表达式检索出满足特定条件的节点信息
void XPathExpression1()
{
Console.WriteLine("select out the book with ID bk103:");
var expr = Navigator.Compile("/catalog/book[@id='bk103']");
var iterator = Navigator.Select(expr);
while(iterator.MoveNext())
{
var nav = iterator.Current.Clone();
Console.WriteLine("Book ID: " + nav.GetAttribute("id", ""));
if(nav.HasChildren)
{
nav.MoveToFirstChild();
do
{
Console.Write("\t{0}:\t{1}\r\n", nav.Name, nav.Value);
} while(nav.MoveToNext());
}
}
}
6. 检索价格大于10的所有图书
void XPathExpression2()
{
Console.WriteLine("select out all books whose price are more than 10:");
var expr = Navigator.Compile("/catalog/book[price>10]");
var iterator = Navigator.Select(expr);
while(iterator.MoveNext())
{
var nav = iterator.Current.Clone();
Console.WriteLine("Book ID: " + nav.GetAttribute("id", ""));
if(nav.HasChildren)
{
nav.MoveToFirstChild();
do
{
if(nav.Name == "title")
{
Console.Write("\t{0}:\t{1}\r\n", nav.Name, nav.Value);
}
if(nav.Name == "price")
{
Console.Write("\t{0}:\t{1}\r\n", nav.Name, nav.Value);
}
} while(nav.MoveToNext());
}
}
}
7. 统计图书的平均价格
void XPathExpression3()
{
Console.WriteLine("calculate the average price of all books:");
var expr = Navigator.Compile("sum(/catalog/book/price) div count(/catalog/book/price)");
var averagePrice = Navigator.Evaluate(expr).ToString();
Console.WriteLine("The average price of the books are {0}", averagePrice);
}
这是xpath的基本使用方法，关键是要灵活使用表达式进行查询。