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Introduction To XML

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What is XML?

  1. XML stands for Extensible Markup Language.
  2. XML is a markup language much like HTML.
  3. XML was designed to carry the data but not to display it.
  4. XML tags are not predefined. You must define your own tags.
  5. XML is designed to be self-descriptive.

Why XML is popular?

  1. Our machines are now only capable of processing requirements of this data format.
  2. It supports data processing, data storage, and bandwidth requirements for the exchange of XML documents.
  3. Driving force for the use of a technology, like XML, is the desire to exchange information in Open Systems or Open Software.
  4. Development of the internet.


  1. XML is text (Unicode) based; Takes up less space; Can be transmitted efficiently.
  2. One XML document can be displayed differently in different media, like HTML, video, CD, DVD. You only have to change the XML document in order to change all the rest.
  3. XML documents can be modularized and its parts can be reused.

SGML (Standard Generalized Markup Language)

  1. Forefather of all markup languages.
  2. In 1969, it Introduced the notion that data processing and document processing could be one and the same thing.
  3. Introduced the notion of a generalized document format.
  4. SGML specification can communicate between systems.
  5. Provides DTD specification to improve the standard of the document.

Example of an HTML Document

  1. <html>  
  2. <head><title>Example</title></head.  
  3. <body>  
  4. <h1>This is an example of a page.</h1>  
  5. <h2>Some information goes here.</h2>  
  6. </body>  
  7. </html>  


Write the HTML code in notepad and save it with .html extension(EX:sample.html). Click the file to run in the browser.



  1. <?xml version=“1.0”/>  
  2. <mymessage>  
  3. <message> Welcome to XML </message>  
  4. </mymessage>  

An XML document contains one root element and its child elements.

Example of an XML Document

  1. <?xml version=“1.0”/>  
  2. <address>  
  3. <name>Alice Lee</name>  
  4. <email></email>  
  5. <phone>212-346-1234</phone>  
  6. <birthday>1985-03-22</birthday>  
  7. </address>  


The XML code will be written in the XML copy editor. Save it at any location (EX:text.xml). Click it and open in the browse.



output(The XML program output)



Difference Between HTML and XML 

  1. HTML tags have a fixed meaning and browsers know what it is while the XML tags are different for different applications, and users know what they mean.
  2. HTML tags are used for display while the XML tags are used to describe the documents and the data.

Benefits of XML

  1. Simplifies Data Sharing.
  2. Simplifies Data Transport.
  3. Simplifies Platform Changes.
  4. Separates Data from HTML.
  5. Makes Your Data More Available.
  6. Represents the information and the metadata about the information.
  7. XML is referred as future-proof or loosely coupled, since it has the capability of separating process and data content.
  8. XML is used to create new internet languages.

Well-Formed Documents

  1. An XML document is said to be well-formed if it follows all the rules.
  2. An XML parser is used to check that all the rules have been obeyed.
  3. Parser is a software to process XML Document.
  4. It reads the XML Document, Checks its syntax, reports errors and allows programmatic access to documents contents.
  5. XML document is considered well formed if the syntax is correct.
  6. Single root, start and end tag, attribute values in quotes.
  7. Recent browsers such as Internet Explorer 5 and Netscape 7 come with XML parsers.
  8. Parsers are also available for free download over the Internet. One is Xerces, from the Apache open-source project.
  9. Java 1.4 also supports an open-source parser.

Advantages of xml over sgml

  1. Though XML is using most of the functionality in SGML, it provides a number of distinct advantages.
  2. XML permits well-formed documents to be parsed without the need for a DTD, whereas SGML implementations require some DTD for processing
  3. XML is much simpler and more permissive in its syntax than SGML.
  4. Implementation of SGML over the internet is more difficult than in XML.

Advantages of XML over HTML (and differences)

  1. XML is not a replacement for HTML.
  2. XML and HTML were designed with different goals:
  3. XML was designed to transport and store data, with focus on what data is.
  4. HTML was designed to display data, with focus on how data looks.
  5. HTML is about displaying information, while XML is about carrying information.

Advantages of xml over EDI(Electronic Data Interchange)

  1. XML requires less cost for data transaction and maintenance than EDI (which uses Millions of dollars for transactions).
  2. XML uses Internet for data exchange whereas EDI over Internet does not meet much success.
  3. XML has many built in components like validity checking, data mapping, Extensible style sheet etc.,
  4. XML supports internationalization and localization but EDI doesn’t provide it.

Drawbacks of XML

  1. XML is huge – takes lot of space to represent data (3 to 20 times greater than file formats).
  2. XML editors often lack the detail and helpfulness found in common EDI editors.


  1. A well-formed document has a tree structure and obeys all the XML rules.
  2. A particular application may add more rules in either a DTD (document type definition) or in a schema.
  3. Many specialized DTDs and schemas have been created to describe particular areas.
  4. These range from disseminating news bulletins (RSS) to chemical formulas.
  5. DTDs were developed first, so they are not as comprehensive as schema.

Thanks for reading.

posted Jan 12 by Shivaranjini

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  1. XML document has a single root node.
  2. The tree is a general ordered tree.
  3. A parent node may have any number of children.
  4. Child nodes are ordered and may have siblings.
  5. Preorder traversals are usually used to get the information, out of the tree.


Simple XML Document

  1. <?xml version = “1.0” ?> <address>  
  2. <name>  
  3. <first>Alice</first></br>  
  4. <last>Lee</last></br>  
  5. </name>  
  6. <email></email></br>  
  7. <phone>123-45-6789</phone></br>  
  8. <birthday>  
  9. <year>1983</year></br>  
  10. <month>07</month></br>  
  11. <day>15</day>  
  12. </birthday>  
  13. </address>  

Program Demo 

Write the code from XMLCopyEditor.

Save Any Location(EX:Sample.xml). 






Introduction to XPath

XPath can be thought of as a query language such as SQL. However, rather than extracting information from a database, it extracts information from an XML document. XPath is a language for retrieving from a database, it extracts information from an XML document. XPath is a language for retrieving information from a XML document. XPath is used to navigate through elements and attributes in an XML document. Thus, XPath allows identifying parts of an XML document.

XPath provides a common syntax as shown in figure:-


  • XSLT: XSLT is a language for transforming XML documents into XML, HTML, or text.
  • XQuery: XQuery builds on XPath and is a language for extracting from XML documents.

Benefits of XPath

XPath is desingned for XML documents. It provides a single syntax that you can use for queries, addressing, and patterns. XPath is concise, simple, and powerful.

XPath has many benefits:

  • Syntax is simple for the simple and common cases
  • Any path that can occur in an XML document and any set of conditions for the nodes in the path can be specified.
  • Any node in an XML document can be uniquely identified

XPath is designed to be used in many contexts. It is applicable to providing links to nodes, for searching repositories, and for many other applications.


There are many different techniques to use by which you can create an XML document in C#. One of them is LINQ to XML which we are going to discuss in this article.

Let’s say we need to create an XML as below:

  1. <?xml version="1.0" encoding="UTF-8"?>  
  2. <Parent>  
  3. <Header>  
  4. <FileDetails>  
  5. <FileName>RandomFile</FileName>  
  6. <FileVersion>1.0</FileVersion>  
  7. </FileDetails>  
  8. </Header>  
  9. <Body>  
  10. <Infos>  
  11. <Info Type="Information1">This is Information1</Info>  
  12. <Info Type="Information2">This is Information2</Info>  
  13. </Infos>  
  14. <Users>  
  15. <UserDetails>  
  16. <Name>  
  17. <FirstName>Vipul</FirstName>  
  18.  <MiddleName/>  
  19.                     <LastName>Malhotra</LastName>  
  20.                 </Name>  
  21. <DateOfBirth>12-Apr-1990</DateOfBirth>  
  22. </UserDetails>  
  23. </Users>  
  24. </Body>  

Let’s break the creation of the file in two parts so as to be able to see more features.

We will first create the below Xml:

  1. <?xml version="1.0" encoding="UTF-8"?>  
  2. <Parent>  
  3. <Header>  
  4. <FileDetails>  
  5. <FileName>RandomFile</FileName>  
  6. <FileVersion>1.0</FileVersion>  
  7. </FileDetails>  
  8. </Header>  
  9. <Body>  
  10. <Infos>  
  11. <Info Type="Information1">This is Information1</Info>  
  12. <Info Type="Information2">This is Information2</Info>  
  13. </Infos>  
  14. </Body>  

In order to create this, we will first define an XDocument with the parent root as below:

  1. XDocument doc = new XDocument(new XElement("Parent"));  

After this, we will use this “doc” as the root of the file and will writing nested XElement to it.

Let’s first create the Header portion of the xml.
Please notice that the XElement “Header “ is added as a new element and the further elements are added as nested to this “Header” element. It is due to the reason that the elements are sub-elements of “Header”. Further “FileName” and “FileVersion” element is a sub-element of “FileDetails”

In the same way, we would add another section to the root of the doc. This section would be “Body”. 

The code for the same would be as:
This follows the same logic that “Body” is also sub-node of the root “parent” and so it is added directly to the root. Whereas , the element “Infos” is sub-element of “Body” and is so added in the way above. Same goes for “Info” which is a further sub-element of “Infos”. 

Also notice how an attribute is added to each of the “Info” element using XAttribute.

After this, we further need to add the below section as sub-nodes of “Body” and not the root of the application:

  1. <Users>  
  2. <UserDetails>  
  3. <Name>  
  4. <FirstName>Vipul</FirstName>  
  5.  <MiddleName/>  
  6.                     <LastName>Malhotra</LastName>  
  7.                 </Name>  
  8. <DateOfBirth>12-Apr-1990</DateOfBirth>  
  9. </UserDetails>  
  10. </Users>  

In order to do that, we would make sure that the code starts appending the code inside the “Body” tag of the already created xml.

Using XDocument, we can search for the node “Body” and then start adding node XElements to it .
Searching a node Is done using:

Further adding more elements to it is done using the below code:
The logic behind the hierarchy is the same as that discussed above.

The code can also be used inside a loop in case we need to add many similar sections to a particular node. Like in this case there can be many users and all of their details would have to be added in different UserDetails section inside the “Body” node.


This article describes how to transform the XML output of SQL query statements using FOR XML AUTO to HTML using XSLT.

Normally, we execute the query using ExecuteNonQuery statement and fill the output into a data table. We can access the data in the data table by giving column name and row number in the looping method. This makes us work on extra coding and takes a lot of time to get the correct data from executed query. So, I moved to XML because, in XML, we can fetch the values easily and quickly without writing too much code.     

FOR XML Clause in SQL

Basically, we have four types of FOR XML clause in SQL.


Each of the above types satisfies its own need. When you want full control over the produced XML, you use FOR XML EXPLICIT, but it is difficult to understand, read, or maintain. FOR XML AUTO produces the most readable SELECT statement. The RAW option is rarely used and therefore not discussed. The PATH option allows you to mix attributes and elements easier. Here, I gona use FOR XML AUTO.

Table Name - Contact_Details


If we want the output as in XML format, we need to add the FOR XML AUTO statement.


  1. SELECT * FROM Contact_Details FOR XML AUTO  

This query gives the output like,

  1. < Contact_Details Contact_ID=’001’ Contact_Number=’ 088888888’ Contact_Name=’Mohan’ Contact_Location=’Chennai’/>  
  2. < Contact_Details Contact_ID=’002’ Contact_Number=’ 099999999’ Contact_Name=’Abilash’ Contact_Location=’Bangalore’/>  

The XML which we got in output is not in user-friendly format. We need each field as an attribute so, that we can access the values using XPATH. To achieve that, we need to add the ELEMENTS parameter with the query.



This query gives the output like,

  1. < Contact_Details>  
  2.     <Contact_ID>001</Contact_ID>  
  3.     <Contact_Number>088888888</Contact_Number>  
  4.     <Contact_Name>Mohan</Contact_Name>  
  5.     <Contact_Location>Chennai</Contact_Location>  
  6. </ Contact_Details>  
  7. < Contact_Details>  
  8.     <Contact_ID>002</Contact_ID>  
  9.     <Contact_Number>099999999</Contact_Number>  
  10.     <Contact_Name>Abilash</Contact_Name>  
  11.     <Contact_Location>Bangalore</Contact_Location>  
  12. </ Contact_Details>  

So, this is the exact XML format we need.

Now, we are going to create XML DOCUMENT and write this output XML into that XML document in coding. To read the query in XML format, we need to execute the query using ExecuteXmlReader() function. 

  1. XmlReader XMLReader = new XmlReader();  
  2. XmlDocument XmlDoc = new XmlDocument();  
  3. SqlCommand Cmd = new SqlCommand(Query, Conn);  
  4. XMLReader = cmd.ExecuteXmlReader();  
  5. XPathDocument xPathDoc = new XPathDocument(XMLReader);  
  6. XPathNavigator xPathNavi = xPathDoc.CreateNavigator();  
  7. XmlDoc.LoadXml(XpathNavi.OuterXml);  

Now, we got the full structured XML Document. Using this, we will transform the data into HTML format using XSLT.

Before transforming, we need to create one XSLT file to assign the values from XMLDocument to HTML format.


  1. <?xml version=”1.0” encoding=”utf-8”?>  
  2. <xsl:stylesheet version=”1.0” xmlns:xsl=””>  
  3.     <xsl:output method=”xml” indent=”yes” omit-xml-declaration=”yes”>  
  4.         <xsl:template match=”/*”>  
  5.             <table>  
  6.                 <tr>// Column heading  
  7.                     <td>ContactID</td>  
  8.                     <td>ContactNumber</td>  
  9.                     <td>ContName</td>  
  10.                     <td>ContactLocation</td>  
  11.                 </tr>  
  12.                 <xsl:for-each select=”/ Contact_Details”>  
  13.                     <tr>// inserting XML data into HTML table  
  14.                         <td>  
  15.                             <xsl:value-of select=”/Contact_details/Contact_ID” </td> // using XPath we can access the value from XML Document  
  16.                                 <td>  
  17.                                     <xsl:value-of select=”/Contact_details/Contact_Number” </td>  
  18.                                 <td>  
  19.                               <xsl:value-of select=”/Contact_details/Contact_Name” </td>  
  20.                           <td>  
  21.                        <xsl:value-of select=”/Contact_details/Contact_Location” </td>  
  22.                     </tr>  
  23.                 </xsl:for-each>  
  24.             </table>  
  25.         </xsl:template>  
  26. </xsl:stylesheet>  

Now, we have XML Document and XSLT file. In the next step, we are going to transform the XML Document into HTML using XSLT. To do this, we pass the XMLDocument and XSLT file to separate functions and get fully formed HTML strings in return.

  1. Public static string TransformXMLTOHTML(XmlDocument XMLDoc, String XSLTFilename) {  
  2.     StringWriter HTMLString = new StringWriter();  
  3.     XslCompiledTransform Xmltransform = new XslCompiledTransform();  
  4.     XmlTransform.Load(XSLTFilename); // Load XSLT File  
  5.     Xmltranform.Transform(XMLDoc, null, Result); // transform XML into HTML  
  6.     Return HTMLString.ToString();  
  7. }  
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