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


Type: System.String
The namespace prefix of the attribute.
Type: System.String
The local name of the attribute.
Type: System.String
The namespace URI of the attribute.
Type: System.String
The value of the attribute.


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


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


The localName or ns is null.

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.

StringBuilder output = new StringBuilder();

using (XmlWriter writer = XmlWriter.Create(output))
    // Write the root element.

    // 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.

    // Write the XML to file.

OutputTextBlock.Text = output.ToString();


Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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