一、命名空间
System.Xml.Linq.dll 程序集定义了三个命名空间：System.Xml.Linq, System.Xml.Schema 和 System.Xml.XPath
最核心的是 System.Xml.Linq， 定义了对应 XML 文档个方面的很多类型
|
Member of System.Xml.Linq |
Meaning in Life |
|
XAttribute |
Represents an XML attribute on a given XML element |
|
XComment |
Represents an XML comment |
|
XDeclaration |
Represents the opening declaration of an XML document |
|
XDocument |
Represents the entirety of an XML document |
|
XElement |
Represents a given element within an XML document |
|
XName |
Provide a very simple manner to define and reference XML namespaces |
二、编程方式创建XML文档
以前的 .NET XML编程模型需要使用很多冗长的 DOM API，而 LINQ to XML 则完全可以用与 DOM 无关的方式与 XML 文档交互。这样不但大大减少了代码行，而且这种编程模型可以直接映射到格式良好的XML文档结构。
|
static void CreateFunctionalXmlElement() { // A "functional" approach to build an // XML element in memory. XElement inventory = new XElement("Inventory", new XElement("Car", new XAttribute("ID", "1"), new XElement("Color", "Green"), new XElement("Make", "BMW"), new XElement("PetName", "Stan") ) ); // Call ToString() on our XElement. Console.WriteLine(inventory); } |
在内存
中创建XML文档
|
static void CreateFunctionalXmlDoc() { XDocument inventoryDoc = new XDocument( new XDeclaration("1.0", "utf-8", "yes"), new XComment("Current Inventory of AutoLot"), new XElement("Inventory", new XElement("Car", new XAttribute("ID", "1"), new XElement("Color", "Green"), new XElement("Make", "BMW"), new XElement("PetName", "Stan") ), new XElement("Car", new XAttribute("ID", "2"), new XElement("Color", "Pink"), new XElement("Make", "Yugo"), new XElement("PetName", "Melvin") ) ) ); // Display the document and save to disk. Console.WriteLine(inventoryDoc); inventoryDoc.Save("SimpleInventory.xml"); } |
三、使用 LINQ 查询创建XML文档
|
static void CreateXmlDocFromArray() { // Create an anonymous array of anonymous types. var data = new [] { new { PetName = "Melvin", ID = 10 }, new { PetName = "Pat", ID = 11 }, new { PetName = "Danny", ID = 12 }, new { PetName = "Clunker", ID = 13 } }; // Now enumerate over the array to build // an XElement. XElement vehicles = new XElement("Inventory", from c in data select new XElement("Car", new XAttribute("ID", c.ID), new XElement("PetName", c.PetName) ) ); Console.WriteLine(vehicles); } |
四、加载和解析XML内容
|
static void LoadExistingXml() { // Build an XElement from string. string myElement = @" Yellow Yugo "; XElement newElement = XElement.Parse(myElement); Console.WriteLine(newElement); Console.WriteLine(); // Load the SimpleInventory.xml file. XDocument myDoc = XDocument.Load("SimpleInventory.xml"); Console.WriteLine(myDoc); } |
六、遍历内存中的XML文档
XML示例：
| <? xml version = " 1.0 " encoding = " utf-8 " ?> < Inventory > < Car carID = " 0 " > < Make > Ford </ Make > < Color > Blue </ Color > < PetName > Chuck </ PetName > </ Car > < Car carID = " 1 " > < Make > VW </ Make > < Color > Silver </ Color > < PetName > Mary </ PetName > </ Car > < Car carID = " 2 " > < Make > Yugo </ Make > < Color > Pink </ Color > < PetName > Gipper </ PetName > </ Car > < Car carID = " 55 " > < Make > Ford </ Make > < Color > Yellow </ Color > 862 CHAPTER 24 n PROGRAMMING WITH THE LINQ APIS < PetName > Max </ PetName > </ Car > < Car carID = " 98 " > < Make > BMW </ Make > < Color > Black </ Color > < PetName > Zippy </ PetName > </ Car > </ Inventory > |
加载
|
static void Main(string[] args) { Console.WriteLine("***** Fun with LINQ to XML *****/n"); // Load the Inventory.xml document into memory. XElement doc = XElement.Load("Inventory.xml"); // We will author each of these next PrintAllPetNames(doc); Console.WriteLine(); GetAllFords(doc); Console.ReadLine(); } |
遍历
|
static void PrintAllPetNames(XElement doc) { var petNames = from pn in doc.Descendants("PetName") select pn.Value; foreach (var name in petNames) Console.WriteLine("Name: {0}", name); } |
查询
|
static void GetAllFords(XElement doc) { var fords = from c in doc.Descendants("Make") where c.Value == "Ford" select c; foreach (var f in fords) Console.WriteLine("Name: {0}", f); } |
七、修改 XML文档
static void AddNewElements(XElement doc)
{
// Add 5 new purple Fords to the incoming document.
for (int i = 0; i < 5; i++)
{
// Create a new XElement
XElement newCar =
new XElement("Car", new XAttribute("ID", i + 1000),
new XElement("Color", "Green"),
new XElement("Make", "Ford"),
new XElement("PetName", "")
);
// Add to doc.
doc.Add(newCar);
}
// Show the updates.
Console.WriteLine(doc);
}