Detecting files that won't open

Hello All,

Does anyone know of a method to automatically detect if a file is
corrupted ?
Due to a failed backup process a number of files were corrupted. The
files are mostly .xls, .doc, .pdf. When you try to open the file, a
dialog box opens stating that the file cannot be opened.

I need to log which files wont open properly, and I'm hoping there is
a way to automate the process.

I've tried using a streamreader to read the contents of the file,
hoping that an exception would be thrown if the file could not
properly be opened...this didn't work.

I've tried opening the file using the Process and ProcessStartInfo
classes, hoping that an exception would be thrown if the file did not
open correctly..this didn't work

The best I've come up with is a console app, which opens each file in
a specified directory, one-at-a-time, pauses for 10 seconds, and then
prompts the user to enter Y for corrupted or N for okay. Files which
elicit a Y response are logged as corrupted.

This approach requires user-input and ideally, I'd like to completely
automate the process. i.e, specifiy a directory and then press go and
read the log when the program completes.

Any ideas appreciated