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XmlTextWriter::LookupPrefix Method (String^)

 

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:
virtual String^ LookupPrefix(
	String^ ns
) override

Parameters

ns
Type: System::String^

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.

Exception Condition
ArgumentException

ns is either null or String.Empty.

System_CAPS_noteNote

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.

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 );
}

.NET Framework
Available since 1.1
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