Adding multiple namespace declarations in XmlWriter

Question

I am trying to write out the following element using XmlWriter

Answer 1

writer.WriteAttributeString("xmlns","gx", null, "http://www.google.com/kml/ext/2.2");
writer.WriteAttributeString("xmlns","kml", null, "http://www.opengis.net/kml/2.2");
writer.WriteAttributeString("xmlns","atom", null, "http://www.w3.org/2005/Atom");

Got that from https://msdn.microsoft.com/en-us/library/cfche0ka(v=vs.100).aspx.