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XmlWriter.WriteProcessingInstruction Method

When overridden in a derived class, writes out a processing instruction with a space between the name and text as follows: <?name text?>.

Namespace: System.Xml
Assembly: System.Xml (in system.xml.dll)

public abstract void WriteProcessingInstruction (
	string name,
	string text
)
public abstract void WriteProcessingInstruction (
	String name, 
	String text
)
public abstract function WriteProcessingInstruction (
	name : String, 
	text : String
)
Not applicable.

Parameters

name

The name of the processing instruction.

text

The text to include in the processing instruction.

Exception typeCondition

ArgumentException

The text would result in a non-well formed XML document.

name is either a null reference (Nothing in Visual Basic) or String.Empty.

This method is being used to create an XML declaration after WriteStartDocument has already been called.

This method can be used to write the XML declaration (rather than WriteStartDocument). This could result in the encoding attribute being incorrectly written. For example, the following C# code would result in an invalid XML document because the default encoding is UTF-8.

XmlWriter writer = XmlWriter.Create("output.xml");
writer.WriteProcessingInstruction("xml", "version='1.0' encoding='UTF-16'");
writer.WriteStartElement("root");
writer.Close();

If text is either a null reference (Nothing in Visual Basic) or String.Empty, this method writes a ProcessingInstruction with no data content, for example <?name?>.

If text contains an invalid sequence of "?>", the XmlWriter can either throw an ArgumentException (XmlTextWriter objects) or insert a space "? >" to avoid writing invalid XML (XmlWriter objects created by the Create method).

The following example writes an XML file representing a book.

using System;
using System.IO;
using System.Xml;

public class Sample {

  private const string filename = "sampledata.xml";

  public static void Main() {
  
     XmlWriterSettings settings = new XmlWriterSettings();
     settings.Indent = true;
     XmlWriter writer = XmlWriter.Create(filename, settings);

     // Write the Processing Instruction node.
     String PItext="type=\"text/xsl\" href=\"book.xsl\"";
     writer.WriteProcessingInstruction("xml-stylesheet", PItext);

     // Write the DocumentType node.
     writer.WriteDocType("book", null , null, "<!ENTITY h \"hardcover\">");
        
     // Write a Comment node.
     writer.WriteComment("sample XML");
    
     // Write the root element.
     writer.WriteStartElement("book");

     // Write the genre attribute.
     writer.WriteAttributeString("genre", "novel");
    
     // Write the ISBN attribute.
     writer.WriteAttributeString("ISBN", "1-8630-014");

     // Write the title.
     writer.WriteElementString("title", "The Handmaid's Tale");
              
     // Write the style element.
     writer.WriteStartElement("style");
     writer.WriteEntityRef("h");
     writer.WriteEndElement(); 

     // Write the price.
     writer.WriteElementString("price", "19.95");

     // Write CDATA.
     writer.WriteCData("Prices 15% off!!");

     // Write the close tag for the root element.
     writer.WriteEndElement();
             
     writer.WriteEndDocument();

     // Write the XML to file and close the writer.
     writer.Flush();
     writer.Close();  
  }

}

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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