change xml namespace - namespaces

Question

I have an xml file as following:
<?xml version="1.0" encoding="utf-8"?>
<ABC version="1" xmlns="urn:Company">
</ABC>
I am releasing version 2 and the namespace changed to "NewCompany".
How do you update the namespace?
I tried
XmlDocument xmlDocument = new XmlDocument();
using (XmlReader xmlReader = XmlReader.Create("myfile.xml"))
{
xmlDocument.Load(xmlReader);
}
XmlNodeList nodeList = xmlDocument.GetElementsByTagName("ABC");
if (nodeList.Count == 1)
{
XmlElement element = nodeList.Item(0) as XmlElement;
if (element != null)
{
element.SetAttribute("xmlns", "NewCompany");
XmlWriterSettings settings = new XmlWriterSettings();
settings.Indent = true;
using (XmlWriter writer = XmlWriter.Create("myfile.xml", settings))
{
xmlDocument.WriteTo(writer);
}
}
}
But I get
"The prefix '' cannot be redefined from to within the same start element tag."
exception

Answer 1

I ran into this today and found a workaround. If you use XmlTextWriter instead of XmlWriter, the problem goes away. Your code sample would look something like this:
XmlNodeList nodeList = xmlDocument.GetElementsByTagName("ABC");
if (nodeList.Count == 1)
{
XmlElement element = nodeList.Item(0) as XmlElement;
if (element != null)
{
element.SetAttribute("xmlns", "NewCompany");
using (XmlTextWriter writer = new XmlTextWriter("myfile.xml", Encoding.UTF8))
{
writer.Formatting = Formatting.Indented;
xmlDocument.WriteTo(writer);
}
}
}
I'd have imagined that XmlWriter.Create will simply return a XmlTextWriter, but that doesn't seem to be the case. From looking around in Reflector, XmlWriter.Create seems to return concrete types different from XmlTextWriter.
XmlTextWriter seems to support changing the namespace of the document element, while the writer returned by XmlWriter.Create doesn't.
I realize that this question is four years old, but perhaps my answer will help someone.