[Original] Introduction to Linq (I): This article will show you the world of linq to xml in minutes, and show you how to use linqxml.

[Original] Introduction to Linq (I): This article will show you the world of linq to xml in minutes, and show you how to use linqxml.

Getting started with Linq (1): takes you to the world of linq to xml in minutes

1. Introduction to Linq

2. Cases of Linq

• Create a file

• Add

• Delete

• Change

• Query

1. Introduction to Linq:

　　Language Integrated Query is a set of extensions for c # and Visual Basic languages. It allows you to write C # Or Visual Basic code to query memory data in the same way as a database. On the Internet, there are many criticisms or praises for the performance or other aspects of Linq. Here, I don't want to comment on any aspect of Linq, because I always believe that the advantages and disadvantages of Iot products are inevitable. In addition, there are many technologies, such as Linq and multithreading. I think that since these technologies exist, they all have their own principles. Determine whether to introduce these technologies based on the needs of your project. Technology itself is born to serve projects.

This blog will take you through a few simple and traditional examples of adding, deleting, modifying, and querying to fully enjoy the fun of linq.

 

2. Cases of Linq

 

Create a file

　　

1 // create a file path 2 string path = string. format (@ "F :\{ 0 }. xml ", DateTime. now. toString ("yyyyMMddhhmmss"); 3 FileInfo fiXML = new FileInfo (path); 4 // if the file does not exist 5 if (! (FiXML. exists) 6 {7 // create xml Document 8 XDocument xelLog = new XDocument (9 new XDeclaration ("1.0", "UTF-8", "no "), 10 new XElement ("ipmsg", 11 new XElement ("msg_log", 12 new XElement ("user", "monkey"), 13 new XElement ("logdate", DateTime. now. toString ("yyyyMMddhhmmss"), 14 new XElement ("message", "") 15) 16) 17); 18 xelLog. save (path); 19}

 

The xml file after running should be like this:

　　

1 <? Xml version = "1.0" encoding = "UTF-8" standalone = "no"?> 2 <ipmsg> 3 <msg_log> 4 <user> monkey brother </user> 5 <logdate> 20150421024045 </logdate> 6 <message> monkey brother traveled here </message> 7 </msg_log> 8 </ipmsg>

 

Add

1 string path = @ "F: \ 20150421024045.xml"; 2 // check whether the File exists 3 if (File. exists (path) 4 {5 // instantiate XMLog 6 XElement xelem = XElement. load (path); 7 8 // execute the linq add (xmlLOG) 9 XElement newLog = new XElement ("msg_log", 10 new XElement ("user", "sashan "), 11 new XElement ("logdate", DateTime. utcNow. toString (), 12 new XElement ("message", ", ") 13); 14 xelem. add (newLog); 15 // save xml16 xelem. save (path); 17 18}

The xml file after running should be like this:

　　

1 <? Xml version = "1.0" encoding = "UTF-8"?> 2 <ipmsg> 3 <msg_log> 4 <user> monkey brother </user> 5 <logdate> 20150421024045 </logdate> 6 <message> monkey brother traveled here </message> 7 </msg_log> 8 <msg_log> 9 <user> Sha Seng </user> 10 <logdate> 4/21/2015 6:49:03 AM </logdate> 11 <message>, the master was captured by monsters </message> 12 </msg_log> 13 </ipmsg>

Delete

 

1 string path = @ "F: \ 20150421024045.xml"; 2 // check whether the File exists 3 if (File. exists (path) 4 {5 // instantiate XMLog 6 XElement xelem = XElement. load (path); 7 8 var queryXML = from xmlLog in xelem. descendants ("msg_log") 9 where xmlLog. element ("user "). value = "monkey" 10 select xmlLog; 11 12 queryXML. remove (); 13 14 // save xml15 xelem. save (path); 16 17}

 

The xml file after running should be like this:

 

1 <? Xml version = "1.0" encoding = "UTF-8"?> 2 <ipmsg> 3 <msg_log> 4 <user> Sha Seng </user> 5 <logdate> 4/21/2015 6:49:03 AM </logdate> 6 <message>, the master was captured by monsters </message> 7 </msg_log> 8 </ipmsg>

 

Change

1 string path = @ "F: \ 20150421024045.xml"; 2 // check whether the File exists 3 if (File. exists (path) 4 {5 // instantiate XMLog 6 XElement xelem = XElement. load (path); 7 8 var queryXML = from xmlLog in xelem. descendants ("msg_log") 9 where xmlLog. element ("user "). value = "Sha Seng" 10 select xmlLog; 11 queryXML. firstOrDefault (). element ("message "). value = "second brother, Master brother captured by monsters"; 12 13 // save xml14 xelem. save (path); 15 16}

 

The xml file after running should be like this:

1 <? Xml version = "1.0" encoding = "UTF-8"?> 2 <ipmsg> 3 <msg_log> 4 <user> Sha Seng </user> 5 <logdate> 4/21/2015 6:49:03 AM </logdate> 6 <message> Senior Engineer 2, </message> 7 </msg_log> 8 </ipmsg>

Query

 

1 string path = @ "F: \ 20150421024045.xml"; 2 string messageByShaSeng = string. empty; 3 // check whether the File exists 4 if (File. exists (path) 5 {6 // instantiate XMLog 7 XElement xelem = XElement. load (path); 8 var queryXml = from xmlLog in xelem. descendants ("msg_log") 9 // All records named Bin 10 where xmlLog. element ("user "). value = "Sha Seng" 11 12 select xmlLog; 13 messageByShaSeng = queryXml. firstOrDefault (). element ("message "). value; 14} 15 16 Console. writeLine (messageByShaSeng );

 

The input content is: Brother 2, Master, captured by monsters

 

 

　　All content in this article is original. You are welcome to read and explore it. Please indicate the source for reprinting. Otherwise, you will be held legally responsible.(Although linq is already an example, it is also original)

We hereby declare that all comments and private messages will be replied immediately. You are also welcome to correct the mistakes and make progress together. In addition, if you want to learn more about Linq, you may wish to take a look at it here.

 

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