I believe File.Exists is only for files, so that will always fail? I think you want Directory.Exists? (Unless you just snipped some code out that was altering path to be to a file)
Other than that, are you wondering if that will work with a Modern/Metro/Windows Store App? I think it will, but the best thing to do would be to just whip up a quick template store app with that code. If you are asking if that will work on a standard win8 desktop app, then I think that will work just fine.