XmlTextWriter.LookupPrefix(String) XmlTextWriter.LookupPrefix(String) XmlTextWriter.LookupPrefix(String) XmlTextWriter.LookupPrefix(String) Method

Definizione

Restituisce il prefisso più vicino definito nell'ambito dello spazio dei nomi corrente per l'URI dello spazio dei nomi.Returns the closest prefix defined in the current namespace scope for the namespace URI.

public:
 override System::String ^ LookupPrefix(System::String ^ ns);
public override string LookupPrefix (string ns);
override this.LookupPrefix : string -> string
Public Overrides Function LookupPrefix (ns As String) As String

Parametri

ns
String String String String

URI dello spazio dei nomi di cui si desidera individuare il prefisso.Namespace URI whose prefix you want to find.

Restituisce

Prefisso corrispondente.The matching prefix. oppure null se non viene individuato un URI dello spazio dei nomi corrispondente nell'ambito corrente.Or null if no matching namespace URI is found in the current scope.

Eccezioni

ns è null o String.Empty.ns is either null or String.Empty.

Esempi

Nell'esempio seguente viene scritto un libro.The following example writes out a book.

#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 );
}

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);  

  }

}
Option Strict
Option Explicit

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
End Class

Commenti

Nota

A partire da .NET Framework 2,0, è consigliabile creare XmlWriter istanze usando il XmlWriter.Create metodo e la XmlWriterSettings classe per sfruttare le nuove funzionalità.Starting with the .NET Framework 2.0, we recommend that you create XmlWriter instances by using the XmlWriter.Create method and the XmlWriterSettings class to take advantage of new functionality.

Si applica a