Date: 02/11/09 (C Sharp)    Keywords: html, xml

I'm trying to write XHTML to an XmlWriter. I'm having trouble generating the standard line:
http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">

With "writer" as my XmlWriter I have
writer.WriteStartElement("html");
writer.WriteAttributeString("xmlns", "http://www.w3.org/1999/xhtml");
writer.WriteAttributeString("lang", "en");
writer.WriteAttributeString("xml:lang", "en");

but writer.WriteAttributeString("xmlns", "http://www.w3.org/1999/xhtml") generates an XmlException: "The prefix '' cannot be redefined from '' to 'http://www.w3.org/1999/xhtml' within the same start element tag."

What am I missing? How do I get that namespace defined?

TIA.

Source: https://csharp.livejournal.com/101629.html