XmlWriter.LookupPrefix(String) XmlWriter.LookupPrefix(String) XmlWriter.LookupPrefix(String) XmlWriter.LookupPrefix(String) Method

定義

在衍生類別中覆寫時,傳回最接近命名空間 URI 在目前命名空間範圍中定義的前置詞。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);
abstract member LookupPrefix : string -> string
Public MustOverride Function LookupPrefix (ns As String) As String

參數

ns
String String String String

您要尋找其前置詞的命名空間 URI。The namespace URI whose prefix you want to find.

傳回

命名空間前置詞;如果在目前範圍中找不到符合的命名空間 URI,則為 nullThe matching prefix or null if no matching namespace URI is found in the current scope.

例外狀況

nsnullString.Emptyns is either null or String.Empty.

在先前的非同步作業完成前呼叫了 XmlWriter 方法。An XmlWriter method was called before a previous asynchronous operation finished. 在此情況下,會擲回 InvalidOperationException 與「非同步作業已經在進行中」的訊息。In this case, InvalidOperationException is thrown with the message "An asynchronous operation is already in progress."

範例

下列範例會寫出一本書。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
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 'Main 
End Class 'Sample

適用於