Linq To Xml 之XDocument, XElement的使用

0. 准备：products.xml的定义：

<?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 加载XML文件

通过XDocument，XElement的Load方法读入XML文件，进行XDocument和XElement的初期化。

XElement elem = XElement.Load(@"D:/VisualStudioProject2008/Test/Linq2XML01/products.xml");  

Console.WriteLine(elem);    

XDocument doc = XDocument.Load(@"D:/VisualStudioProject2008/Test/Linq2XML01/products.xml"); 

 Console.WriteLine(doc.ToString());  

1.2 选择处理

如下代码所示，通过Linq对xml进行查询。

XElement products = XElement.Load(@"D:/VisualStudioProject2008/Test/Linq2XML01/products.xml");    

var query = from p in products.Elements("product")          

where (string)p.Attribute("category") == "book"          

select new          

{              

ID = (string)p.Attribute("id"),              

Name = (string)p.Element("name"),              

Price = (decimal)p.Element("price")         

 };   

 foreach (var item in query)  

{      

Console.WriteLine(item);  

}    

执行结果如下：

{ ID = product1, Name = Programing Something, Price = 2000 }
{ ID = product2, Name = Administrating Something, Price = 5000 } 

更复杂的应用，比如：通过Join一个String数组（书类型的集合）来查询。 

view plainvar categories = new string[] { "book", "novel" };    

 // 在on里直接写p.Element("category")是无法编译通过的， 

 // 必须显示转换为string类型之后比较：(string) p.Element("category")   

 var query = from p in products.Elements("product")                 

let xCategory = (string) p.Attribute("category")                 

join c in categories                   

on xCategory equals c                

orderby xCategory                 

select new                

{                     

Name = (string)p.Element("name"),                     

Price = (decimal)p.Element("price"),                     

Category = xCategory                 

 };    

 foreach (var item in query)    

 {          

Console.WriteLine(item);     

}    

执行结果：

{ 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 }