You can't create an instance of a static class. The whole reason it is static is because you don't need to do so, since all properties and methods are static.
I suspect you want to make FileInfo non-static (and its properties as well).
P.S. I would add that the System.IO namespace has a class called FileInfo, which you might want to consider using instead. http://msdn.microsoft.com/en-GB/library/system.io.fileinfo.aspx