Using WriteXml method, I created an xml file.
MyDs.WriteXml("MyXml", XmlWriteMode.IgnoreSchema)

The first two lines of MyXml are :
(?xml version="1.0" standalone="yes" ?)
(MyDs xmlns="http://www.tempuri.org/MyDs.xsd")

I notice that using XPath for defining parts of an XML document does not return the correct results until I deleted (xmlns="http://www.tempuri.org/MyDs.xsd") from the MyXml.

Any idea why?