XmlWriter.LookupPrefix(String) Metod

Definition

Namnområde:
System.Xml
Sammansättningar:
System.Xml.dll, System.Xml.ReaderWriter.dll
Sammansättningar:
netstandard.dll, System.Xml.ReaderWriter.dll
Sammansättning:
System.Xml.ReaderWriter.dll
Sammansättning:
System.Xml.dll
Sammansättning:
netstandard.dll
Källa:
XmlWriter.cs
Källa:
XmlWriter.cs
Källa:
XmlWriter.cs
Källa:
XmlWriter.cs
Källa:
XmlWriter.cs

När det åsidosätts i en härledd klass returnerar det närmaste prefixet som definierats i det aktuella namnområdesomfånget för namnområdes-URI:n.

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

Parametrar

ns
String

Den namnområdes-URI vars prefix du vill hitta.

Returer

String

Det matchande prefixet eller null om ingen matchande namnområdes-URI hittas i det aktuella omfånget.

Undantag

ArgumentException

ns är antingen null eller String.Empty.

InvalidOperationException

En XmlWriter metod anropades innan en tidigare asynkron åtgärd slutfördes. I det här fallet InvalidOperationException genereras meddelandet "En asynkron åtgärd pågår redan".

Exempel

I följande exempel skrivs en bok ut.

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

Gäller för