XmlWriter::LookupPrefix Method (String^)
When overridden in a derived class, returns the closest prefix defined in the current namespace scope for the namespace URI.
Assembly: System.Xml (in System.Xml.dll)
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.
| Exception | Condition |
|---|---|
| ArgumentException | ns is either null or String.Empty. |
| InvalidOperationException | An XmlWriter method was called before a previous asynchronous operation finished. In this case, InvalidOperationException is thrown with the message “An asynchronous operation is already in progress.” |
The following example writes out a book.
#using <System.Xml.dll> using namespace System; using namespace System::IO; using namespace System::Xml; public ref class Sample { private: static String^ m_Document = L"sampledata.xml"; public: static void Main() { XmlWriter^ writer = nullptr; try { XmlWriterSettings^ settings = gcnew XmlWriterSettings; settings->Indent = true; writer = XmlWriter::Create( m_Document,settings ); writer->WriteComment( L"sample XML fragment" ); // Write an element (this one is the root). writer->WriteStartElement( L"book" ); // Write the namespace declaration. writer->WriteAttributeString( L"xmlns", L"bk", nullptr, L"urn:samples" ); // Write the genre attribute. writer->WriteAttributeString( L"genre", L"novel" ); // Write the title. writer->WriteStartElement( L"title" ); writer->WriteString( L"The Handmaid's Tale" ); writer->WriteEndElement(); // Write the price. writer->WriteElementString( L"price", L"19.95" ); // Lookup the prefix and write the ISBN element. String^ prefix = writer->LookupPrefix( L"urn:samples" ); writer->WriteStartElement( prefix, L"ISBN", L"urn:samples" ); writer->WriteString( L"1-861003-78" ); writer->WriteEndElement(); // Write the style element (shows a different way to handle prefixes). writer->WriteElementString( L"style", L"urn:samples", L"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 != nullptr ) writer->Close(); } } }; void main() { Sample::Main(); }
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1