How to parse XML address verification response from USPS in VB.NET?

http://www.vbdotnetheaven.com/UploadFile/shehperu/SimpleXMLParser11152005073044AM/SimpleXMLParser.aspx
http://www.codeproject.com/KB/cpp/parsefilecode.aspx
http://msdn.microsoft.com/en-us/library/aa468547.aspx

The examples, although staightforward, seem to require an XML file path.  I already have the USPS XML string (file contents) in a variable.  How can I use the examples with my variable contents instead of a file path?
Thanks.

http://msdn.microsoft.com/en-us/library/1af7xa52.aspx

XMLTextReader can take a file as input, or a STRING.

I have read the link you provided, but it appears to me that XMLTextReader expects a file name (file path) and not a string variable.

What I have been working with is the following, but I need to parse the XML contents of a string variable instead of an XML file ("H:\Sample.xml").

Dim xDoc As XmlDocument = New XmlDocument()
xDoc.Load("H:\Sample.xml")
Dim Address1 As XmlNodeList = xDoc.GetElementsByTagName("Address1")
Dim Address2 As XmlNodeList = xDoc.GetElementsByTagName("Address2")
Dim City1 As XmlNodeList = xDoc.GetElementsByTagName("City")
Dim ST1 As XmlNodeList = xDoc.GetElementsByTagName("State")
Dim Zip1 As XmlNodeList = xDoc.GetElementsByTagName("Zip5")
Dim Zip2 As XmlNodeList = xDoc.GetElementsByTagName("Zip4")
MessageBox.Show(Address2(0).InnerText & Constants.vbLf & _
                        City1(0).InnerText & ", " & ST1(0).InnerText & " " & _                       Zip1(0).InnerText & "-" & Zip2(0).InnerText)

This code works great, but it won't handle a string variable instead of a file name.  I can change it to use the XMLTextReader, but I don't see how it would work either.  Can you provide and example of how to do as I have done above but with XMLTextReader.

Works very well with the code I am using to extract the nodes.  Thanks.