Linq To Xml 备忘录2（X* 类的使用）

Linq To XML 中使用到的以X开头的类都在 System.Xml.Linq 命名空间下。如下图所示：

 

XObject
    |-XAttribute
    |-XNode
        |-XComment
        |-XContainer
        |    |-XElement
        |    |-XDocument
        |-XDocumentType
        |-XProcessingInstruction
        |-XText
             |-XCData

 

另外比较有用的类：XStreamElement 用于处理大数据量的XML，以提高性能。

 

1. XML文档作成：

利用 XDocument, XElement, XAttribute, XDeclaration 作成XML。

public static void CreateXDocument()
{
System.Xml.Linq.XDocument doc = CreateTestXDocument();
doc.Save(@"D:/temp/CreateXDocument.xml");
Console.WriteLine(doc.ToString());
}
public static XDocument CreateTestXDocument()
{
System.Xml.Linq.XDocument doc =
new XDocument(
new XDeclaration("1.0", "UTF-8", "yes"),
new XElement("Product",
new XAttribute("id", "RX78"),
new XAttribute("operator", "amuro"),
new XElement("name", "Gundam"),
new XElement("price", "1000"),
new XElement("material", "gundarium")
)
);
return doc;
}

 

将会输出下面的结果：

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<Product id="RX78" operator="amuro">
<name>Gundam</name>
<price>1000</price>
<material>gundarium</material>
</Product>

 

2. 通过 XNamespace 指定命名空间

public static void TestXNamespace()
{
XNamespace ns = "http://ns.handcraft.org/testnamespace";
XElement e = new XElement(ns + "product", new XAttribute("id", "RX78"),
new XElement(ns + "name", "Gundam"), new XElement("append", "nonamespace"));
Console.WriteLine("默认Namespace：");
Console.WriteLine(e);

Console.WriteLine(e.Name);

XNamespace ns1 = "http://ns.handcraft.org/testnamespace";
XElement e1 = new XElement(ns1 + "product",new XAttribute(XNamespace.Xmlns + "e1", ns), new XAttribute("id", "RX78"),
new XElement(ns1 + "name", "Gundam"), new XElement("append", "nonamespace"));
Console.WriteLine("先头追加Namespace:");
Console.WriteLine(e1);
}

 

将会输出以下结果：

默认Namespace:
<product id="RX78" xmlns="http://ns.handcraft.org/testnamespace">
<name>Gundam</name>
<append xmlns="">nonamespace</append>
</product>
{http://ns.handcraft.org/testnamespace}product
先头追加Namespace:
<e1:product xmlns:e1="http://ns.handcraft.org/testnamespace" id="RX78">
<e1:name>Gundam</e1:name>
<append>nonamespace</append>
</e1:product>

 

3. XPathEvaluate, XPathSelectElements (这些是扩展方法，命名空间：System.Xml.XPath)

通过 XPathEvaluate, XPathSelectElements 使用XPath功能。

下面是示例的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>

 

XPathEvalute的使用示例：

public static void XPathEvaluate()
{
XElement products = XElement.Load(@"D:/temp/products.xml");
var result = (IEnumerable<Object>) products.XPathEvaluate("/product[@category='book']/name/text()");
foreach (var item in result)
{
Console.WriteLine(item);
}
}

结果如下：

Programing Something
Administrating Something

 

XPathSelectElements的使用示例：

public static void XPathSelect()
{
XElement products = XElement.Load(@"D:/temp/products.xml");
var query = from c in products.XPathSelectElements("/product[@category='book']")
orderby (string) c.Element("name")
select c;
foreach (var item in query)
{
Console.WriteLine(item);
}
}

 

结果如下：

<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="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>