Writing XML File using XmlWriter//Reading XML Files//Reading XML File using XmlDocument//Inserting Data to an XML Document
The XmlWriter and XmlTextWriter classes are defined in the System.XML namespace.
The XmlTextWriter class is derived from XmlWriter class, which represents a writer that provides fast non-cached forward-only way of generating XML documents based on the W3C Extensible Markup Language (XML) 1.0 specification.
In this article, I will show you how to use XmlTextWriter class to create an XML document and write data to the document.
Adding namespace Reference
Since Xml classes are defined in the System.XML namespace, so first thing you need to do is to Add the System.XML reference to the project.
using System.Xml;
Creating an XML Document
The constructor of the XmlTextWriter class creates an XML file if file doesn't exist. In this sample, I create a new XML file called xmltest.xml in C\temp directory.
XmlTextWriter writer = new XmlTextWriter("C:\\temp\\xmltest.xml", null);
NOTE: If you don't want to write data in an XML file and want to display XML contents on the Console, pass Console.Out as a parameter of the constructor.
XmlTextWriter writer = new XmlTextWriter(Console.Out);
Adding Data to the Document
The WriteStartDocument method starts a new document. The WriteStartElement and the WriteEndElement pair is used to add a new element to the document. The WriteString writes a string to the document.
writer.WriteStartDocument();
writer.WriteComment("Commentss: XmlWriter Test Program");
writer.WriteProcessingInstruction("Instruction","Person Record");
writer.WriteStartElement("p", "person", "urn:person");
writer.WriteStartElement("LastName","");
writer.WriteString("Chand");
writer.WriteEndElement();
writer.WriteElementInt16("age","", 25);
writer.WriteEndDocument();
Souce Code: Attachment createxml1.cs 2 KB
namespace WriteToXML
{
using System;
using System.Xml;
/// <summary>
/// Summary description for Class1.
/// </summary>
public class Class1
{
public Class1()
{
}
public static int Main(string[] args)
{
try
{
// Creates an XML file is not exist
XmlTextWriter writer = new XmlTextWriter("C:\\temp\\xmltest.xml", null);
// Starts a new document
writer.WriteStartDocument();
//Write comments
writer.WriteComment("Commentss: XmlWriter Test Program");
writer.WriteProcessingInstruction("Instruction","Person Record");
// Add elements to the file
writer.WriteStartElement("p", "person", "urn:person");
writer.WriteStartElement("LastName","");
writer.WriteString("Chand");
writer.WriteEndElement();
writer.WriteStartElement("FirstName","");
writer.WriteString("Mahesh");
writer.WriteEndElement();
writer.WriteElementInt16("age","", 25);
// Ends the document
writer.WriteEndDocument();
}
catch (Exception e)
{
Console.WriteLine ("Exception: {0}", e.ToString());
}
return 0;
}
}
}
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The XmlReader and XmlTextReader classes are defined in the System.XML namespace.
The XmlTextReader class is derived from XmlReader class. The XmlTextReader class can be used to read the XML documents. The read function of this document reads the document until end of its nodes.
In this article, I will show you how to use XmlTextReader class to read an XML document and write data to the console.
Adding namspace Reference
Since Xml classes are defined in the System.XML namespace, so first thing you need to do is to Add the System.XML reference to the project.
using System.Xml;
Open an XML Document
The constructor of the XmlTextReader class opens an XML file. In this sample, I used an XML file called xmltest.xml in C\temp directory. You can download the attached file.
// Open an XML file
XmlTextReader reader = new XmlTextReader("C:\\temp\\xmltest.xml");
Reading Data
The Read method of the XmlTextReader class reads the data.
while ( reader.Read() )
{
Console.WriteLine(reader.Name);
}
Souce Code: Attachment readxml1.cs 1 KB, xmltest.xml 1 KB
namespace ReadXML
{
using System;
using System.Xml;
/// <summary>
/// Summary description for Class1.
/// </summary>
public class Class1
{
public Class1()
{
}
public static int Main(string[] args)
{
try
{
// Open an XML file
XmlTextReader reader = new XmlTextReader("C:\\temp\\xmltest.xml");
while ( reader.Read() )
{
Console.WriteLine(reader.Name);
}
}
catch (Exception e)
{
Console.WriteLine ("Exception: {0}", e.ToString());
}
return 0;
}
}
}
------------------------------------------------------------------------------------------------------------------
Suppose I have following XML fragment:
<Authors>
<Author>
<FirstName>John</FirstName>
<LastName>Doe</LastName>
</Author>
<Author>
<FirstName>Jane</FirstName>
<LastName>Eod</LastName>
</Author>
</Authors>
Now, how can I loop through my collection of authors and for each author retrieve its first and last name and put them in a variable strFirst and strLast?
- - - XMLApp.cs
using System;
using System.Xml;
public class XMLApp
{
public void YourMethod( String strFirst, String strLast)
{
// Do something with strFirst and strLast.
// ...
Console.WriteLine( "{0}, {1}", strLast, strFirst);
}
public void ProcessXML( String xmlText)
{
XmlDocument _doc = new XmlDocument( );
_doc.LoadXml( xmlText);
// alternately, _doc.Load( _strFilename); to read from a file.
XmlNodeList _fnames = _doc.GetElementsByTagName( "FirstName" );
XmlNodeList _lnames = _doc.GetElementsByTagName( "LastName" );
// I'm assuming every FirstName has a LastName in this example, your requirements may vary. //
for ( int _i = 0; _i < _fnames.Count; ++_i )
{
YourMethod( _fnames[ _i].InnerText,
_lnames[ _i].InnerText );
}
public static void Main( String[] args)
{
XMLApp _app = new XMLApp( );
// Passing XML text as a String, you can also use the
// XMLDocument::Load( ) method to read the XML from a file.
//
_app.ProcessXML( @" <Authors>
<Author>
<FirstName>John</FirstName>
<LastName>Doe</LastName>
</Author>
<Author>
<FirstName>Jane</FirstName>
<LastName>Eod</LastName>
</Author>
</Authors> " );
}
} // end XMLApp
- - - XMLApp.cs
Remember to /reference the System.Xml.dll on the command-line to build XMLApp.cs:
csc.exe /r:System.Xml.dll XMLApp.cs
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The XmlNode and the XmlDocument classes can be used to insert XML data to an existing document or to a new document.
Adding namspace Reference
Since Xml classes are defined in the System.XML namespace, so first thing you need to do is to Add the System.XML reference to the project.
using System.Xml;
Loading XML to Document
LoadXml method of XmlDocument can be used to load XML data to a document or to load an existing XML document..
// Load XML data to a document
XmlDocument doc = new XmlDocument();
doc.LoadXml("<XMLFile>" +
" <SomeData>Old Data</SomeData>" +
"</XMLFile>");
Inserting XML Data
The below code inserts XML data to the file and saves file as InsertedDoc.xml.
Souce Code:
try
{
XmlNode currNode;
XmlDocument doc = new XmlDocument();
doc.LoadXml("<XMLFile>" +
" <SomeData>Old Data</SomeData>" +
"</XMLFile>");
XmlDocumentFragment docFrag = doc.CreateDocumentFragment();
docFrag.InnerXml="<Inserted>" +
" <NewData>Inserted Data</NewData>" +
"</Inserted>";
// insert the availability node into the document
currNode = doc.DocumentElement.FirstChild;
currNode.InsertAfter(docFrag, currNode.LastChild);
//save the output to a file
doc.Save("InsertedDoc.xml");
}
catch (Exception e)
{
Console.WriteLine ("Exception: {0}", e.ToString());
}
output of the code looks like this -
<XMLFile>
<SomeData>
Old Data
<Inserted>
<NewData>Inserted Data</NewData>
</Inserted>
</SomeData>
</XMLFile>