Linq初级班 Linq To XML体验(高级编程篇)
首先,我们在Linq初级班 Linq To XML体验(基础)和Linq初级班 Linq To XML体验(编程篇)了解了一些XML的基本知识以及如何用LINQ to XML对XML文档进行简单的操作,本文将继续深入LINQ to XML,做一些高级编程的演示.我也是LINQ的初学者,文章中不免会有一些不对的地方,希望高手们多多指点,为我们LINQ初学者们多提宝贵的意见,我也会继续努力的,本文章目录如下所示:
1.Linq to XML函数构造
函数构造是指通过单个语句构建XML树的能力.在Linq初级班 Linq To XML体验(编程篇)中我们已经体验了如何使用XElement和XAttribute类手工创建XML树,也可以通过其他XElement和XAttribute对象传递给XElement类的构造函数来创建子元素和属性,也就是说,LINQ查询的结果可以用来创建XML树,下面就来看看一个演示:
代码
//-----------------------------------------------------------
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person",
new XElement("Name", "Huang Cong"),
new XElement("Sex", "男"),
new XElement("Age", 22)),
new XElement("Person",
new XElement("Name", "Li Si"),
new XElement("Sex", "女"),
new XElement("Age", 12))
));
//通过LINQ查询将xel的元素添加至新的XElement中
XElement newXel = new XElement(new XElement("NewRoot",
new XElement("Persons",
xel.Elements().Where(u => u.Name == "Person").Select(u => u)
)));
Console.WriteLine(newXel);
}
}
}
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person",
new XElement("Name", "Huang Cong"),
new XElement("Sex", "男"),
new XElement("Age", 22)),
new XElement("Person",
new XElement("Name", "Li Si"),
new XElement("Sex", "女"),
new XElement("Age", 12))
));
//通过LINQ查询将xel的元素添加至新的XElement中
XElement newXel = new XElement(new XElement("NewRoot",
new XElement("Persons",
xel.Elements().Where(u => u.Name == "Person").Select(u => u)
)));
Console.WriteLine(newXel);
}
}
}
运行结果:
2.Linq to XML批注
LINQ to XML批注是指将一个对象添加或关联到一个XML节点或者属性,批注可以是任何类型的任何对象,可以通过XElement或XAttribute类的AddAnnotation方法来添加批注,需要注意的是:当调用AddAnnotation方法时,是将一个新的对象添加至相应的元素或属性上,原先绑定的批注并不会被删除掉,如果想删除批注,可以调用RemoveAnnotations方法:
代码
//-----------------------------------------------------------
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
public class Test
{
public int Id { get; set; }
public string Info { get; set; }
}
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person", "Huang Cong")));
//为元素添加2个批注
xel.Element("Person").AddAnnotation(new Test() { Id = 1, Info = "测试1" });
xel.Element("Person").AddAnnotation(new Test() { Id = 2, Info = "测试2" });
Console.WriteLine("为元素添加2个批注:");
var query = xel.Element("Person").Annotations<Test>().Select(u => u);
foreach (var q in query)
{
Console.WriteLine(q.Info);
}
Console.WriteLine("-------------------------------------");
//删除所有批注
xel.Element("Person").RemoveAnnotations<Test>();
Console.WriteLine("删除所有批注:");
query = xel.Element("Person").Annotations<Test>().Select(u => u);
foreach (var q in query)
{
Console.WriteLine(q.Info);
}
Console.WriteLine("-------------------------------------");
}
}
}
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
public class Test
{
public int Id { get; set; }
public string Info { get; set; }
}
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person", "Huang Cong")));
//为元素添加2个批注
xel.Element("Person").AddAnnotation(new Test() { Id = 1, Info = "测试1" });
xel.Element("Person").AddAnnotation(new Test() { Id = 2, Info = "测试2" });
Console.WriteLine("为元素添加2个批注:");
var query = xel.Element("Person").Annotations<Test>().Select(u => u);
foreach (var q in query)
{
Console.WriteLine(q.Info);
}
Console.WriteLine("-------------------------------------");
//删除所有批注
xel.Element("Person").RemoveAnnotations<Test>();
Console.WriteLine("删除所有批注:");
query = xel.Element("Person").Annotations<Test>().Select(u => u);
foreach (var q in query)
{
Console.WriteLine(q.Info);
}
Console.WriteLine("-------------------------------------");
}
}
}
运行结果:
3.Linq to XML轴
LINQ to XML提供了对XML的查询功能,以查找特定的元素或者属性并返回它们的值,LINQ to XML的轴方法让你可以轻松实现以上的功能,LINQ to XML还提供了返回个别节点的方法,这可以让开发人员处理更细粒度的细节.下面是几个主要的轴方法:
1. Descendants和DescendantsAndSelf
2. Ancestors和AncestorsAndSelf
3. ElementsAfterSelf和ElementBeforeSelf
下面分别给各个方法做示例讲解:
3.1 Descendants和DescendantsAndSelf
Descendants方法返回指定元素的后继元素的集合,不包括元素本身,而DescendantsAndSelf则包括元素本身.
代码
//-----------------------------------------------------------
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person",
new XElement("Name", "Huang Cong"),
new XElement("Age", 22)),
new XElement("Person",
new XElement("Name", "Li Si"),
new XElement("Age", 12))
));
Console.WriteLine("遍历所有元素:");
var des = xel.Descendants();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("遍历所有名称为Person的元素,不包括本身:");
des = xel.Descendants("Person").Descendants();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("遍历所有名称为Person的元素,包括本身:");
des = xel.Descendants("Person").DescendantsAndSelf();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
}
}
}
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person",
new XElement("Name", "Huang Cong"),
new XElement("Age", 22)),
new XElement("Person",
new XElement("Name", "Li Si"),
new XElement("Age", 12))
));
Console.WriteLine("遍历所有元素:");
var des = xel.Descendants();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("遍历所有名称为Person的元素,不包括本身:");
des = xel.Descendants("Person").Descendants();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("遍历所有名称为Person的元素,包括本身:");
des = xel.Descendants("Person").DescendantsAndSelf();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
}
}
}
运行结果:
3.2 Ancestors和AncestorsAndSelf
Ancestors方法返回指定节点的上级元素,不包括元素本身,而AncestorsAndSelf则包括元素本身.
代码
//-----------------------------------------------------------
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person",
new XElement("Name", "Huang Cong"))
));
Console.WriteLine("遍历所有元素:");
var des = xel.Descendants();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("遍历所有名称为Name的元素的上级元素集合,不包括本身:");
des = xel.Element("Person").Element("Name").Ancestors();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("遍历所有名称为Name的元素的上级元素集合,包括本身:");
des = xel.Element("Person").Element("Name").AncestorsAndSelf();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
}
}
}
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person",
new XElement("Name", "Huang Cong"))
));
Console.WriteLine("遍历所有元素:");
var des = xel.Descendants();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("遍历所有名称为Name的元素的上级元素集合,不包括本身:");
des = xel.Element("Person").Element("Name").Ancestors();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("遍历所有名称为Name的元素的上级元素集合,包括本身:");
des = xel.Element("Person").Element("Name").AncestorsAndSelf();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
}
}
}
运行结果:
3.3 ElementsAfterSelf和ElementBeforeSelf
ElementsAfterSelf方法和ElementBeforeSelf方法分别返回指定元素之后的元素和值指定元素之前的元素,也可以指定条件返回指定的元素集合.
代码
//-----------------------------------------------------------
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person",
new XElement("Name", "Huang Cong"),
new XElement("Sex","男"),
new XElement("Age",12)))
);
Console.WriteLine("获取Name元素之后的元素集合:");
var des = xel.Element("Person").Element("Name").ElementsAfterSelf();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("获取Name元素之后的名为Sex的元素集合:");
des = xel.Element("Person").Element("Name").ElementsAfterSelf("Sex");
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("获取Age元素之前的元素集合:");
des = xel.Element("Person").Element("Age").ElementsBeforeSelf();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("获取Age元素之前的名为Sex的元素集合:");
des = xel.Element("Person").Element("Age").ElementsBeforeSelf("Sex");
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
}
}
}
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person",
new XElement("Name", "Huang Cong"),
new XElement("Sex","男"),
new XElement("Age",12)))
);
Console.WriteLine("获取Name元素之后的元素集合:");
var des = xel.Element("Person").Element("Name").ElementsAfterSelf();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("获取Name元素之后的名为Sex的元素集合:");
des = xel.Element("Person").Element("Name").ElementsAfterSelf("Sex");
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("获取Age元素之前的元素集合:");
des = xel.Element("Person").Element("Age").ElementsBeforeSelf();
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
Console.WriteLine("获取Age元素之前的名为Sex的元素集合:");
des = xel.Element("Person").Element("Age").ElementsBeforeSelf("Sex");
foreach (var d in des)
{
Console.WriteLine(d);
}
Console.WriteLine("----------------------------------");
}
}
}
运行结果:
4.Linq to XML事件
在对XML树进行修改的时候,LINQ to XML事件会提供通知,LINQ to XML提供了2个事件来响应XML树的修改:Changing和Changed.当修改XML树时这2个时间会相继被触发.从运行结果我们可以看出,更新动作实际上是一个删除操作加上一个添加完成的:
代码
//-----------------------------------------------------------
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person",
new XElement("Name", "Huang Cong"),
new XElement("Sex","男"),
new XElement("Age",12)))
);
xel.Changing += new EventHandler<XObjectChangeEventArgs>(xel_Changing);
xel.Changed += new EventHandler<XObjectChangeEventArgs>(xel_Changed);
//修改Person元素的Age元素值
xel.Element("Person").SetElementValue("Age", 22);
}
static void xel_Changed(object sender, XObjectChangeEventArgs e)
{
Console.WriteLine("触发Changed事件:");
Console.WriteLine("ChangedValue:{0} \tObjectChange:{1}", ((XNode)sender).ToString(), e.ObjectChange);
Console.WriteLine("------------------------------------");
}
static void xel_Changing(object sender, XObjectChangeEventArgs e)
{
Console.WriteLine("触发Changing事件:");
Console.WriteLine("ChangingValue:{0} \tObjectChange:{1}", ((XNode)sender).ToString(), e.ObjectChange);
Console.WriteLine("------------------------------------");
}
}
}
// All Rights Reserved , Copyright (C) 2010 ,黄聪 , Ltd .
//-----------------------------------------------------------
using System;
using System.Xml.Linq;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
XElement xel = new XElement(new XElement("Root",
new XElement("Person",
new XElement("Name", "Huang Cong"),
new XElement("Sex","男"),
new XElement("Age",12)))
);
xel.Changing += new EventHandler<XObjectChangeEventArgs>(xel_Changing);
xel.Changed += new EventHandler<XObjectChangeEventArgs>(xel_Changed);
//修改Person元素的Age元素值
xel.Element("Person").SetElementValue("Age", 22);
}
static void xel_Changed(object sender, XObjectChangeEventArgs e)
{
Console.WriteLine("触发Changed事件:");
Console.WriteLine("ChangedValue:{0} \tObjectChange:{1}", ((XNode)sender).ToString(), e.ObjectChange);
Console.WriteLine("------------------------------------");
}
static void xel_Changing(object sender, XObjectChangeEventArgs e)
{
Console.WriteLine("触发Changing事件:");
Console.WriteLine("ChangingValue:{0} \tObjectChange:{1}", ((XNode)sender).ToString(), e.ObjectChange);
Console.WriteLine("------------------------------------");
}
}
}
运行结果:
警告:不允许在被触发事件的执行过程中修改XML树,特别不要在事件中修改触发事件发生的节点,因为这会导致不可预测的结果.不过可以在事件中修改另外一个XML树.
小结:
LINQ to XML提供了大量方便的方法和接口给开发人员操作XML文档,这大大的提高了开发效率,希望本章的内容对你有所帮助哈,我也是LINQ的初学者,文章中不免会有一些不对的地方,希望高手们多多指点,为我们LINQ初学者们多提宝贵的意见,我也会继续努力的~~
作者：黄聪
出处：http://www.cnblogs.com/huangcong/
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。
出处：http://www.cnblogs.com/huangcong/
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。
