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XmlWriter.WriteAttributeString Method (String, String, String, String)

When overridden in a derived class, writes out the attribute with the specified prefix, local name, namespace URI, and value.

Namespace:  System.Xml
Assembly:  System.Xml (in System.Xml.dll)
public void WriteAttributeString(
	string prefix,
	string localName,
	string ns,
	string value
)

Parameters

prefix
Type: System.String

The namespace prefix of the attribute.

localName
Type: System.String

The local name of the attribute.

ns
Type: System.String

The namespace URI of the attribute.

value
Type: System.String

The value of the attribute.

ExceptionCondition
InvalidOperationException

The state of writer is not WriteState.Element or writer is closed.

ArgumentException

The xml:space or xml:lang attribute value is invalid.

XmlException

The localName or ns is null.

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.”

This method writes out the attribute with a user defined namespace prefix and associates it with the given namespace. If the prefix is "xmlns" then this method also treats this as a namespace declaration and associates the declared prefix with the namespace URI provided in the given attribute value. In this case the ns argument can be null.

WriteAttributeString does the following:

  • If the attribute value includes double or single quotes, they are replaced with " and ' respectively.

  • If writing an xml:space attribute, the writer verifies the attribute value is valid. (Valid values are preserve or default.)

  • If writing an xml:lang attribute, the writer does not verify that the attribute value is valid according to the W3C XML 1.0 recommendation.

For the asynchronous version of this method, see WriteAttributeStringAsync.

The following example uses the WriteAttributeString method to write a namespace declaration.

using System;
using System.IO;
using System.Xml;

public class Sample {

  public static void Main() {

     XmlWriter writer = null;

     writer = XmlWriter.Create("sampledata.xml");

     // Write the root element.
     writer.WriteStartElement("book");

     // Write the xmlns:bk="urn:book" namespace declaration.
     writer.WriteAttributeString("xmlns","bk", null,"urn:book");

     // Write the bk:ISBN="1-800-925" attribute.
     writer.WriteAttributeString("ISBN", "urn:book", "1-800-925");

     writer.WriteElementString("price", "19.95");

     // Write the close tag for the root element.
     writer.WriteEndElement();

     // Write the XML to file and close the writer.
     writer.Flush();
     writer.Close();  

  }
}

.NET Framework

Supported in: 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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