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XmlWriter.LookupPrefix Method

When overridden in a derived class, returns the closest prefix defined in the current namespace scope for the namespace URI.

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

public abstract string LookupPrefix(
	string ns
)

Parameters

ns
Type: System.String

The namespace URI whose prefix you want to find.

Return Value

Type: System.String
The matching prefix or null if no matching namespace URI is found in the current scope.

ExceptionCondition
ArgumentException

ns is either null or String.Empty.

The following example writes out a book.

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

 public class Sample
 {
   private const string m_Document = "sampledata.xml";

   public static void Main() {

      XmlWriter writer = null;

      try {

        XmlWriterSettings settings = new XmlWriterSettings();
        settings.Indent = true;
        writer = XmlWriter.Create (m_Document, settings);

        writer.WriteComment("sample XML fragment");

        // Write an element (this one is the root).
        writer.WriteStartElement("book");

        // Write the namespace declaration.
        writer.WriteAttributeString("xmlns", "bk", null, "urn:samples");

        // Write the genre attribute.
        writer.WriteAttributeString("genre", "novel");

        // Write the title.
        writer.WriteStartElement("title");
        writer.WriteString("The Handmaid's Tale");
        writer.WriteEndElement();

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

        // Lookup the prefix and write the ISBN element.
        string prefix = writer.LookupPrefix("urn:samples");
        writer.WriteStartElement(prefix, "ISBN", "urn:samples");
        writer.WriteString("1-861003-78");
        writer.WriteEndElement();

        // Write the style element (shows a different way to handle prefixes).
        writer.WriteElementString("style", "urn:samples", "hardcover");

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

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

      finally {
        if (writer != null)
           writer.Close();
     } 
   }

 }
#using <mscorlib.dll>
#using <System.Xml.dll>
using namespace System;
using namespace System::IO;
using namespace System::Xml;

 public __gc class Sample
 {
private:
   static String* m_Document = S"sampledata.xml";

public:
   static void Main() {

      XmlWriter * writer = 0;

      try {

        XmlWriterSettings * settings = new XmlWriterSettings();
        settings->Indent = true;
        writer = XmlWriter::Create (m_Document);

        writer->WriteComment(S"sample XML fragment");

        // Write an element (this one is the root).
        writer->WriteStartElement(S"book");

        // Write the namespace declaration.
        writer->WriteAttributeString(S"xmlns", S"bk", 0, S"urn:samples");

        // Write the genre attribute.
        writer->WriteAttributeString(S"genre", S"novel");

        // Write the title.
        writer->WriteStartElement(S"title");
        writer->WriteString(S"The Handmaid's Tale");
        writer->WriteEndElement();

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

        // Lookup the prefix and write the ISBN element.
        String* prefix = writer->LookupPrefix(S"urn:samples");
        writer->WriteStartElement(prefix, S"ISBN", S"urn:samples");
        writer->WriteString(S"1-861003-78");
        writer->WriteEndElement();

        // Write the style element (shows a different way to handle prefixes).
        writer->WriteElementString(S"style", S"urn:samples", S"hardcover");

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

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

      __finally {
        if (writer != 0)
           writer->Close();
     }
   }
 };

void main(){
	Sample::Main();
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

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