LINQ to XML Memo 1 (use of xdocument and xelement)

0. Preparation: Define products. xml:

<? XML version = "1.0" encoding = "UTF-8"?>
<Products>
<Product ID = "product1" Category = "book">
<Name> programing something </Name>
<Price> 2000 </price>
<Publishdate> 2008/10/10 </publishdate>
<Authors>
<Author> Tarou book </author>
<Author> Hanako book </author>
</Authors>
</Product>
<Product ID = "product2" Category = "book">
<Name> administrating something </Name>
<Price> 5000 </price>
<Publishdate> 2008/10/12 </publishdate>
<Authors>
<Author> kotarou book1 </author>
<Author> kohanako book2 </author>
</Authors>
</Product>
<Product ID = "product3" Category = "novel">
<Name> suspection novel </Name>
<Price> 500 </price>
<Publishdate> 2007/12/12 </publishdate>
<Authors>
<Author> jirou Tarou </author>
</Authors>
</Product>
<Product ID = "product4" Category = "novel">
<Name> fantasy novel </Name>
<Price> 540 </price>
<Publishdate> 2008/9/14 </publishdate>
<Authors>
<Author> Tarou book </author>
</Authors>
</Product>
<Product ID = "product5" Category = "Cram">
<Name> study English </Name>
<Price> 2400 </price>
<Publishdate> 2008/9/14 </publishdate>
<Authors>
<Author> English Tarou </author>
<Author> English jirou </author>
</Authors>
</Product>
</Products>

 

1. LINQ to XML
1.1 load XML files

Use the load method of xdocument and xelement to read XML files and perform initial transformation of xdocument and xelement.

Xelement ELEM = xelement. load (@ "D:/visualstudioproject2008/test/linq2xml01/products. XML "); <br/> console. writeline (ELEM); </P> <p> xdocument Doc = xdocument. load (@ "D:/visualstudioproject2008/test/linq2xml01/products. XML "); <br/> console. writeline (Doc. tostring ());

 

1.2 select processing

As shown in the following code, you can use LINQ to query XML.

Xelement products = xelement. load (@ "D:/visualstudioproject2008/test/linq2xml01/products. XML "); </P> <p> var query = from P in products. elements ("product") <br/> where (string) p. attribute ("category") = "book" <br/> select new <br/>{< br/> id = (string) p. attribute ("ID"), <br/> name = (string) p. element ("name"), <br/> price = (decimal) p. element ("price") <br/>}; </P> <p> foreach (VAR item in query) <br/>{< br/> console. writeline (item); <br/>}

 

The execution result is as follows:

{Id = product1, name = programing something, price = 2000}
{Id = product2, name = administrating something, price = 5000}

 

More complex applications, such as join a String Array (a set of books.

 VaR categories = new string [] {"book", "novel" };< br/> // write P directly in on. element ("category") cannot be compiled. <br/> // It must be displayed and compared after being converted to the string type: (string) p. element ("category") <br/> var query = from P in products. elements ("product") <br/> let xcategory = (string) p. attribute ("category ") <br/> join C in categories <br/> On xcategory equals C <br/> orderby xcategory <br/> select new <br/>{< br/> name = (string) p. element ("name"), <br/> price = (decimal) p. element ("price"), <br/> Category = xcategory <br/>}; <br/> foreach (VAR item in query) <br/> {<br/> console. writeline (item); <br/>}

 

Execution result:

{Name = programing something, price = 2000, Category = book}
{Name = administrating something, price = 5000, Category = book}
{Name = suspection novel, price = 500, Category = novel}
{Name = fantasy novel, price = 540, Category = novel}