I have an XML document that I load in and try to search with XPath. The root node in this file is <t:Transmission xmlns:t='urn:InboundShipment'> and the file end is properly closed with </t:Transmission>.
My problem is that I cannot walk the tree without using a descendant axis. In other words, I can do: SelectSingleNode("//TransactionHeader[SHIPPERSTATE='CA']") and get a node in return. But I cannot do what should be the equivalent: SelectSingleNode("/Transmission/TransmissionBody/Transaction/TransactionHeader[SHIPPERSTATE='CA']")
If I remove the t: I can do an XPath search on /Transmission and get the whole file. With the t: in there I just get null. Or if I try SelectSingleNode("t:Transmission") I get an error with my XPath statement.
I generally do not need to query the root element, so I should be able to make do with just using the descendant axis for my searches. But the XML looks valid to me and so I'd like to know how to address this. Plus I don't want to ask the client to remove "t:" just because I don't know how to deal with it.
The "t:" is a namespace prefix, which is bound to the namespace 'urn:InboundShipment.' In order to properly handle it, you have to tell c# what the prefix is bound to. This page should explain how to use System.Xml.XmlNamespaceManager to handle the namespace.
Edit: See this answer, as well.