Windows Phone 8.0
Dim fs As IO.FileStream = IO.File.OpenRead(MyFolder/MyFile.txt)
Windwos Phone 8.1 WinRTDim fs As System.IO.Stream = Await Windows.ApplicationModel.Package.Current.InstalledLocation.OpenStreamForReadAsync("MyFolder\MyFile.txt")
Apparently in 8.0 one had to use forward slashes "/" and now in 8.1 one must use backslashes "\"; Who would have thought?