Hello, xeroxero!

You can use XML DOM model here and XPath.

So, the code can look like this:
XmlDocument xmlDoc= new XmlDocument();
xmlDoc.Load(xml);

XmlNodeList files = xmlDoc.SelectNodes("directory/file");
foreach(XmlNode file in files)
{
   //create attribute 'size' if it doesn't exist
}

You wrote  on Thu, 02 Nov 2006 11:28:04 -0500:

x> I have an XML document with this as a sample fragment:

x> <?xml version="1.0" encoding="utf-16"?>
x> <directory path="c:\\test\\directory">
x> <file name="fileA.doc" />
x> <file name="fileB.txt" />
x> </directory>

x> I would like to iterate over the document, find any element that is
x> named 'file', and add an attribute 'size' if it doesn't already
x> exist.
x> Can an XPathNavigator be used for that purpose, and if so how? I am
x> not sure about which tool to use, since it seems like I'll modify the
x> collection while it's in-use.

x> Thanks.

--
With best regards, Vadym Stetsyak.
Blog: http://vadmyst.blogspot.com