Hi Peter,
Thanks for posting!
There's no feature in NCrunch that lets you exclude coverage from files based on a wildcard. You're welcome to
request one on uservoice if you like. Right now the exclusions are only handled through the toolbar options on the Metrics Window.
The only other option I can think of would be disable instrumentation for your .xaml.cs files using
code coverage suppression comments, though in your situation I don't think this would be a very attractive approach.