Damaged DNG files: yes - Library -> Validate DNG Files. This will be very robust check *iff* DNG files were not damaged when the validity check codes were computed ;-}. (and this is a good reason to visually inspect all DNG files after import/conversion).
Others - here is a way (there is no direct way that I am aware of):
* Exit Lightroom
* Delete or rename your catalog Previews.lrdata folder.
* Open Lightroom
* Invoke "Library -> Previews -> Build Standard-Sized Previews".
(you'll want to do all files in catalog, presumably)
You'll be presented with a list of files Lr could not build previews for (and an option to 'Show In Library').
Note: whether a damaged file is on that list depends on how it's damaged .
To be clear: there are 2 types of damage - those Lr can detect (e.g. invalid format), and those Lr can't (e.g. legal but wrong raw data). Lr will assign validity check codes to DNGs if it did not detect damage, even if the file is damaged. Likewise, Lr will be able to build a preview for it, if no damage detected, even though the preview may be all white, or have stripes/rectangles on it (which shouldn't be there ).
PS - I wish Lr would assign validity check codes for non-DNG files too, so damage check not limited to DNGs.
PPS - @Lr5, *all* DNGs created by Lightroom (whether raw or not) have validity check codes, however DNGs which do not have the check codes are excluded from the validity check. If I were a DNG user, I'd consider updating all my DNGs to have the check codes - dunno best way to do that.
Thanks again, Rob. You always have great info.