Program flow controlled by catching exceptions

I have a directory on a pc that is watched by a FileSystemWatcher, images that are created with a wireless camera and copied across to the directory. The issue I am having is I need to process the image as soon as it is created, but sometimes the camera software still has a lock on the file and there does not seem to be a way of checking to see if a file is open/writable without first trying to open it, then reacting if it throws an exception.

Another bad practice I am using is a Thread.Sleep() after the exception is thrown, to pause a little longer so the lock on the image is released by the camera software. Ultimately I need to be able to deal with numerous cameras, and I cannot always guarantee that they don't have dodgy software, so an ability to check to see if a file is locked without having to throw an exception would eradicate the way the code is written at present?

I am willing to use C++ and creating a wrapper need be.

I had a similar problem a few years back, with audio files recorded on the microphone into a directory. I spent most of the project cursing the FileSYstemWatcher and its unreliable behavior, and ended up having the FSW watcher code just put the new files' names into a queue, and handle them a second later. Not the most elegant solution, but it works.

Yggdrasil said:

I had a similar problem a few years back, with audio files recorded on the microphone into a directory. I spent most of the project cursing the FileSYstemWatcher and its unreliable behavior, and ended up having the FSW watcher code just put the new files' names into a queue, and handle them a second later. Not the most elegant solution, but it works.

I am loading all the filenames into a queue and doing some processing in a background worker (that is where the exception attempts are caught). I would be nice to have a PriorityQueue where you could attempt other files, then try the failed ones later.

Im also having issues with random duplication so I may have to use a reference list of all files names added in a given session before I add them to a queue. The filesystemwatcher is a pain to code with efficiently, bceause you just end up with loads of code to check events are not raised twice, files are writable and so on.

I really don't like relying on catching exceptions, because if someone has to look at the code I have written, they might start to think I am the worlds worst coder