XmlWriter.LookupPrefix(String) Method
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
When overridden in a derived class, returns the closest prefix defined in the current namespace scope for the namespace URI.
public:
abstract System::String ^ LookupPrefix(System::String ^ ns);
public abstract string LookupPrefix (string ns);
public abstract string? LookupPrefix (string ns);
abstract member LookupPrefix : string -> string
Public MustOverride Function LookupPrefix (ns As String) As String
- ns
- String
The namespace URI whose prefix you want to find.
The matching prefix or null
if no matching namespace URI is found in the current scope.
ns
is either null
or String.Empty
.
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();
}
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();
}
}
}
Option Strict
Option Explicit
Imports System.IO
Imports System.Xml
Public Class Sample
Private Shared m_Document As String = "sampledata.xml"
Public Shared Sub Main()
Dim writer As XmlWriter = Nothing
Try
Dim settings As XmlWriterSettings = 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", Nothing, "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.
Dim prefix As String = 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 Not (writer Is Nothing) Then
writer.Close()
End If
End Try
End Sub
End Class
Produit | Versions |
---|---|
.NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
.NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.6, 2.0, 2.1 |
UWP | 10.0 |
Commentaires sur .NET
.NET est un projet open source. Sélectionnez un lien pour fournir des commentaires :