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XmlTextWriter.LookupPrefix-Methode

Gibt das nächstliegende Präfix zurück, das im aktuellen Namespacebereich für den Namespace-URI definiert ist.

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

Syntax

'Declaration
Public Overrides Function LookupPrefix ( _
    ns As String _
) As String
'Usage
Dim instance As XmlTextWriter
Dim ns As String
Dim returnValue As String

returnValue = instance.LookupPrefix(ns)

public override string LookupPrefix (
    string ns
)

public:
virtual String^ LookupPrefix (
    String^ ns
) override

public String LookupPrefix (
    String ns
)

public override function LookupPrefix (
    ns : String
) : String

Parameter

  • ns
    Der Namespace-URI, dessen Präfix gesucht werden soll.

Rückgabewert

Das passende Präfix. Oder NULL (Nothing in Visual Basic), wenn im aktuellen Gültigkeitsbereich kein übereinstimmender Namespace-URI gefunden wird.

Ausnahmen

Ausnahmetyp Bedingung

ArgumentException

ns ist entweder NULL (Nothing in Visual Basic) oder String.Empty.

Hinweise

Hinweis

Die empfohlene Vorgehensweise für die Version Microsoft .NET Framework, Version 2.0 besteht darin, mithilfe der System.Xml.XmlWriter.Create-Methode und der XmlWriterSettings-Klasse XmlWriter-Instanzen zu erstellen. So können Sie alle neuen Features dieser Version in vollem Umfang nutzen. Weitere Informationen finden Sie unter Erstellen von XML-Writern.

Beispiel

Im folgenden Beispiel wird ein Buch geschrieben.

Option Strict
Option Explicit

Imports System
Imports System.IO
Imports System.Xml

Public Class Sample
    Private Shared filename As String = "sampledata.xml"
    Public Shared Sub Main()
        
        Dim writer As New XmlTextWriter(filename, Nothing)
        'Use indenting for readability.
        writer.Formatting = Formatting.Indented
        
        writer.WriteComment("sample XML fragment")
        
        'Write an element (this one is the root).
        writer.WriteStartElement("bookstore")
        
        'Write the namespace declaration.
        writer.WriteAttributeString("xmlns", "bk", Nothing, "urn:samples")
        
        writer.WriteStartElement("book")
        
        'Lookup the prefix and then write the ISBN attribute.
        Dim prefix As String = writer.LookupPrefix("urn:samples")
        writer.WriteStartAttribute(prefix, "ISBN", "urn:samples")
        writer.WriteString("1-861003-78")
        writer.WriteEndAttribute()
        
        'Write the title.
        writer.WriteStartElement("title")
        writer.WriteString("The Handmaid's Tale")
        writer.WriteEndElement()
        
        'Write the price.
        writer.WriteElementString("price", "19.95")
        
        'Write the style element.
        writer.WriteStartElement(prefix, "style", "urn:samples")
        writer.WriteString("hardcover")
        writer.WriteEndElement()
        
        'Write the end tag for the book element.
        writer.WriteEndElement()
        
        'Write the close tag for the root element.
        writer.WriteEndElement()
        
        'Write the XML to file and close the writer.
        writer.Flush()
        writer.Close()
        
        'Read the file back in and parse to ensure well formed XML.
        Dim doc As New XmlDocument()
        'Preserve white space for readability.
        doc.PreserveWhitespace = True
        'Load the file.
        doc.Load(filename)
        
        'Write the XML content to the console.
        Console.Write(doc.InnerXml)
    End Sub 'Main 
End Class 'Sample

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

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

  public static void Main()
  {

     XmlTextWriter writer = new XmlTextWriter (filename, null);
     //Use indenting for readability.
     writer.Formatting = Formatting.Indented;
        
     writer.WriteComment("sample XML fragment");
    
     //Write an element (this one is the root).
     writer.WriteStartElement("bookstore");

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

     writer.WriteStartElement("book");

     //Lookup the prefix and then write the ISBN attribute.
     string prefix = writer.LookupPrefix("urn:samples");
     writer.WriteStartAttribute(prefix, "ISBN", "urn:samples");
     writer.WriteString("1-861003-78");
     writer.WriteEndAttribute();     

     //Write the title.
     writer.WriteStartElement("title");
     writer.WriteString("The Handmaid's Tale");
     writer.WriteEndElement();
              
     //Write the price.
     writer.WriteElementString("price", "19.95");
     
     //Write the style element.
     writer.WriteStartElement(prefix, "style", "urn:samples");
     writer.WriteString("hardcover");
     writer.WriteEndElement();

     //Write the end tag for the book element.
     writer.WriteEndElement();

     //Write the close tag for the root element.
     writer.WriteEndElement();
             
     //Write the XML to file and close the writer.
     writer.Flush();
     writer.Close();

     //Read the file back in and parse to ensure well formed XML.
     XmlDocument doc = new XmlDocument();
     //Preserve white space for readability.
     doc.PreserveWhitespace = true;
     //Load the file
     doc.Load(filename);
    
     //Write the XML content to the console.
     Console.Write(doc.InnerXml);  

  }

}

#using <System.Xml.dll>

using namespace System;
using namespace System::IO;
using namespace System::Xml;
int main()
{
   String^ filename = "sampledata.xml";
   XmlTextWriter^ writer = gcnew XmlTextWriter( filename, nullptr );
   
   //Use indenting for readability.
   writer->Formatting = Formatting::Indented;
   writer->WriteComment( "sample XML fragment" );
   
   //Write an element (this one is the root).
   writer->WriteStartElement( "bookstore" );
   
   //Write the namespace declaration.
   writer->WriteAttributeString( "xmlns", "bk", nullptr, "urn:samples" );
   writer->WriteStartElement( "book" );
   
   //Lookup the prefix and then write the ISBN attribute.
   String^ prefix = writer->LookupPrefix( "urn:samples" );
   writer->WriteStartAttribute( prefix, "ISBN", "urn:samples" );
   writer->WriteString( "1-861003-78" );
   writer->WriteEndAttribute();
   
   //Write the title.
   writer->WriteStartElement( "title" );
   writer->WriteString( "The Handmaid's Tale" );
   writer->WriteEndElement();
   
   //Write the price.
   writer->WriteElementString( "price", "19.95" );
   
   //Write the style element.
   writer->WriteStartElement( prefix, "style", "urn:samples" );
   writer->WriteString( "hardcover" );
   writer->WriteEndElement();
   
   //Write the end tag for the book element.
   writer->WriteEndElement();
   
   //Write the close tag for the root element.
   writer->WriteEndElement();
   
   //Write the XML to file and close the writer.
   writer->Flush();
   writer->Close();
   
   //Read the file back in and parse to ensure well formed XML.
   XmlDocument^ doc = gcnew XmlDocument;
   
   //Preserve white space for readability.
   doc->PreserveWhitespace = true;
   
   //Load the file
   doc->Load( filename );
   
   //Write the XML content to the console.
   Console::Write( doc->InnerXml );
}

import System.*;
import System.IO.*;
import System.Xml.*;

public class Sample
{
    private static String fileName = "sampledata.xml";

    public static void main(String[] args)
    {
        XmlTextWriter writer = new XmlTextWriter(fileName, null);

        //Use indenting for readability.
        writer.set_Formatting(Formatting.Indented);
        writer.WriteComment("sample XML fragment");

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

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

        //Lookup the prefix and then write the ISBN attribute.
        String prefix = writer.LookupPrefix("urn:samples");
        writer.WriteStartAttribute(prefix, "ISBN", "urn:samples");
        writer.WriteString("1-861003-78");
        writer.WriteEndAttribute();

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

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

        //Write the style element.
        writer.WriteStartElement(prefix, "style", "urn:samples");
        writer.WriteString("hardcover");
        writer.WriteEndElement();

        //Write the end tag for the book element.
        writer.WriteEndElement();

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

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

        //Read the file back in and parse to ensure well formed XML.
        XmlDocument doc = new XmlDocument();

        //Preserve white space for readability.
        doc.set_PreserveWhitespace(true);

        //Load the file
        doc.Load(fileName);

        //Write the XML content to the console.
        Console.Write(doc.get_InnerXml());
    } //main 
} //Sample

Plattformen

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

.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.

Versionsinformationen

.NET Framework

Unterstützt in: 2.0, 1.1, 1.0

.NET Compact Framework

Unterstützt in: 2.0, 1.0

Siehe auch

Referenz

XmlTextWriter-Klasse
XmlTextWriter-Member
System.Xml-Namespace

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