InfoPath Dev

I'm working on infopath forms that will be used through sharepoint.  Because the forms will be web based, I'm having to use visual studio tools for applications (VSTA).  I transferred my code from an existing form with the object code developed in vbscript and found out that the linkage would not work

i.e.  txtUId = XDocument.DOM.selectSingleNode("//my:txtUId")

is there a correct way to link the object variables with the form fields?  Any suggestions are welcome.

In the C# 2003 DOM, it would be thisXDocument.DOM.selectSingleNode("//my:txtUId")

In the C# 2007 DOM, it would be MainDataSource.CreateNavigator.SelectSingleNode("//my:txtUId", NamespaceManager)