Linq to XML 增删改查

Linq to XML同样是对原C#访问XML文件的方法的封装，简化了用xpath进行xml的查询以及增加，修改，删除xml元素的操作。

C#访问XML文件的常用类：XmlDocument，XmlElement，XmlAttribute，XmlNode，XmlText等;
Linq to XML 中的常用类 ：XDocument，XElement，XAttribute。
废话不多说了，直接上代码：
xml文件数据格式如下

publicclassDataBaseInfo

{

publicstring ID {get; set; }

publicstring Company {get;set; }

publicstring Server {get;set; }

publicstring DataBase {get;set; }

publicstring UserName {get;set; }

publicstring Password {get;set; }

privatestaticXDocument doc =new XDocument();

publicstaticstring filePath =".DataBaseInfo.xml";

public DataBaseInfo() {

doc =XDocument.Load(filePath);

}

public DataBaseInfo(string filepath):this()

{

filePath = filepath;

}

///<summary>

///增

///</summary>

///<returns></returns>

publicbool Add()

{

XElement db =new XElement("DataBase",

newXAttribute("id",ID),

newXElement("company",newXAttribute("value",Company)),

newXElement("server",Server)),

newXElement("database",DataBase)),

newXElement("username",UserName)),

newXElement("password",Password))

);

try

{

//用XElement的Add方法

//XElement doc = XElement.Load(filePath);

//doc.Add(db);

//用XDocument的Add方法

doc.Element("DataBases").Add(db);

doc.Save(filePath);

returntrue;

}

catch

{

returnfalse;

}

}

///<summary>

///删

///</summary>

///<param name="id"></param>

///<returns></returns>

publicstaticbool Remove(string id)

{

XElement xe = (from dbin doc.Element("DataBases").Elements("DataBase")where db.Attribute("id").Value == idselect db).Single() asXElement;

try

{

xe.Remove();

doc.Save(filePath);

returntrue;

}

catch

{

returnfalse;

}

}

///<summary>

///改

///</summary>

///<returns></returns>

publicbool Modify()

{

XElement xe = (from dbin doc.Element("DataBases").Elements("DataBase")where db.Attribute("id").Value.ToString() == IDselect db).Single();

try

{

xe.Element("company").Attribute("value").Value = Company;

xe.Element("server").Attribute("value").Value = Server;

xe.Element("database").Attribute("value").Value = DataBase;

xe.Element("username").Attribute("value").Value = UserName;

xe.Element("password").Attribute("value").Value = Password;

doc.Save(filePath);

returntrue;

}

catch

{

returnfalse;

}

}

///<summary>

///查

///</summary>

///<returns></returns>

publicList<DataBaseInfo> GetAll()

{

List<DataBaseInfo> dbs = (from dbin doc.Element("DataBases").Elements("DataBase")

selectnewDataBaseInfo

{

ID = db.Attribute("id").Value.ToString(),

Company = db.Element("company").Attribute("value").Value.ToString(),

Server = db.Element("server").Attribute("value").Value.ToString(),

DataBase = db.Element("database").Attribute("value").Value.ToString(),

UserName = db.Element("username").Attribute("value").Value.ToString(),

Password = db.Element("password").Attribute("value").Value.ToString()

}).ToList();

return dbs;

}

怎么样，如何对之前DOM方式访问XML熟悉的话， 是不是发现简单了不少呢？

xml文件如下：<?xml version="1.0" encoding="UTF-8"?>
<record_info RecordIndex="1" Upload2ShareCenterTimes="1" Upload2ResShareCenter="1" Upload2ShareCenterStatus="2">
<LessonGUID>22DE52E8-3AB6-42DE-9014-2E44B33A0E11</LessonGUID>
<RecTime StartTime="2011-06-15 14:49:36" EndTime="2011-06-15 14:49:51"/>
<CourseName>22</CourseName>
<LessonName>11</LessonName>
<SpeakerName>22</SpeakerName>
<Introduction/>
<ImageIndex>
<Index Name="24008984.jpg" Time="00:00:00"/>
</ImageIndex>
<ChannelInfo Count="4">
<Channel Name="教师桌面" Type="0" ID="0" Resolution="640 480" Quality="60" BandWidth="768" FrameRate="15" Keyframe="100" EncMode="VBR" Deinterlace="0" Denoise="0"/>
<Channel Name="老师通道" Type="1" ID="1" Resolution="640 480" Quality="60" BandWidth="768" FrameRate="25" Keyframe="100" EncMode="CBR" Deinterlace="1" Denoise="1"/>
<Channel Name="学生通道" Type="3" ID="3" Resolution="640 480" Quality="60" BandWidth="768" FrameRate="25" Keyframe="100" EncMode="VBR" Deinterlace="1" Denoise="1"/>
<Channel Name="全景视频" Type="2" ID="2" Resolution="720 576" Quality="60" BandWidth="768" FrameRate="25" Keyframe="100" EncMode="VBR" Deinterlace="1" Denoise="1"/>
</ChannelInfo>
<VidInfo IsRecSM="1" IsRecMM="1" SMFormat="1" MMFormat="2" TotalTime="00:00:12">
<Vid_SM SplitCount="4">
<RecFile Name="20110615144936.iac" Format="1" Channel="-1"/>
</Vid_SM>
<Vid_MM VidSize="720 576">
<RecFile Name="20110615144936_M.wmv" Format="2"/>
</Vid_MM>
</VidInfo>
</record_info>
要求读取<RecFile Name="20110615144936_M.wmv" Format="2"/>该节点中的Name,并要求Format=2
实现代码如下：
public static string GetVideoFile(string url)
{
string videoFilename = null;
//var ss = from e in XDocument.Load(url).Elements("record_info").Elements("Vid_MM").Elements("RecFile")
var query = from c in XDocument.Load(url).Elements("record_info").Elements("VidInfo").Elements("Vid_MM").Elements("RecFile")
where (string)c.Attribute("Format").Value == "2"
select c;
foreach (var book in query)
{
videoFilename=book.Attribute("Name").Value;

}
return videoFilename==null?null:videoFilename;

}

获取元素属性有两个方法，XElement.Attribute() 和XElement.Attributes()

简单举个例就知道了

// we will use this to store a reference to one of the elements in the XML tree. XElement firstParticipant; XDocument xDocument = new XDocument( new XElement("BookParticipants",firstParticipant = new XElement("BookParticipant",new XAttribute("type","Author"),new XElement("FirstName","Joe"),new XElement("LastName","Rattz")))); Console.WriteLine(firstParticipant.Attribute("type").Value);

// we will use this to store a reference to one of the elements in the XML tree. XElement firstParticipant; XDocument xDocument = new XDocument( new XElement("BookParticipants",new XAttribute("experience","first-time"),"Rattz")))); foreach(XAttribute attr in firstParticipant.Attributes()) { Console.WriteLine(attr); }

输出

type="Author"

experience="first-time"

那么往元素上加属性有如下方法

XElement.Add()

XElement.AddFirst()

XElement.AddBeforeThis()

XElement.AddAfterThis()

删除元素属性有如下方法

XAttribute.Remove()

更新元素属性是这样的

XElement.Attribute("someattribute").Value = "beginner"

同样的属性也有XElement.SetAttributeValue() 方法

用起来和XElement.SetElementValue是一样的,这里不举例了