Problem with excluding namespace from XmlWriter.WriteStartElement

Question

I have a little problem that perhaps you can help me with.

I try to use the XmlWriter to write an XML-tag that looks like this ( w3c feed recommendation ):

<atom:link href="http://localhost" rel="self" type="application/rss+xml" />

The problem is that I can't use the WriteStartElement -method as I would want to (atom as a prefix and link as the element name), since this gives me a " ArgumentException: Cannot use a prefix with an empty namespace ".

My code looks like this:

public void WriteTo(XmlWriter writer, Feed feed)
{
    // RSS element
    writer.WriteStartElement("rss", "");
    writer.WriteAttributeString("version", "2.0");
    writer.WriteAttributeString("xmlns", "atom", string.Empty, "http://www.w3.org/2005/Atom");

    // Channel element
    writer.WriteStartElement("channel");

    // The link to the feed.
    writer.WriteStartElement("link", "atom");
    writer.WriteAttributeString("href", feed.FeedUrl.ToString());
    writer.WriteAttributeString("rel", "self");
    writer.WriteAttributeString("type", "application/rss+xml");
    writer.WriteEndElement();

    // Feed information
    writer.WriteElementString("title", feed.Title);
    writer.WriteElementString("description", feed.Description);
    writer.WriteElementString("link", feed.Link.ToString());

    // Iterate through all items.
    foreach (FeedItem item in feed.Items)
    {
        writer.WriteStartElement("item");
        writer.WriteElementString("title", item.Title);
        writer.WriteElementString("link", item.Link.ToString());
        writer.WriteElementString("description", item.Description);
        writer.WriteElementString("guid", item.Guid);
        writer.WriteEndElement();
    }

    // Channel element end
    writer.WriteEndElement();

    // RSS element end
    writer.WriteEndElement();
}

I assume that my problem is trivial and can easily be solved, but how?

UPDATE:

The problem is solved. Check Jon Skeets answer for the solution.

Answer 1

Why not just use the appropriate namespace ( http://www.w3.org/2005/Atom )?

You could write the namespace declaration earlier, in which case you only need the WriteStartElement overload which takes the element name and namespace - I think the prefix is then used automatically.