Why can't I see the XML for my DataSet?

I'm doing the tutorial on msdn for 3 tier architacture.  I've created a Data Set with the designer that's in the App_Code folder.  This is named "Northwind.xsd".  I've created all of the TableAdapters and DataTables which are visible in the designer.
The tutorial says to right click on the DataSet and choose view code to see the XML for this.  When I do this in my project it opens up the blank Northwind.cs file.  I've tried this a couple times but can't view the xml.
What am I doing wrong?  Do I need to set a property or do something else? 
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