How to catch exception when loading .NET WinForm app user.config file?

Question

Sometimes in .NET (2.0) WinForm desktop apps which use the default configuration system, the user.config file will become corrupted and can't be loaded anymore (when the configuration system tries to load it, it'll throw a System.Xml.XmlException).

Putting aside the question of "why did the file get corrupted in the first place" (maybe it was cosmic rays, or HDD problems, or something else you can't control), the question then becomes "how can one catch this exception and do something meaningful with it?

Microsoft's Connect site has a report on this sort of problem. Unfortunately, their report isn't very helpful.

Is it possible to catch exceptions that originate in the default configuration system loader itself? Or would you have to roll your own configuration system to be able to catch this type of exception?

Answer 1

One easy way would be to have a "loader" app that all it does is check if the config file for the real app exists, otherwise create it, and then start the real app.

Might be some neater way of doing it that I'm not aware of though.

Answer 2

There's something wrong - something, probably your application, is writing a blank user.config file. This is a bug to investigate and fix. It may be that your application is not exiting cleanly (so it is sometimes silently wiping the app.config, so I'd start by taking a look at the shutdown sequence. Also, sticking a 3rd party file utility on the file may help you catch see exactly when and where it gets corrupted).

If you can't fix the problem, then the best workaround I can think of is to use an independent XML configuration file (ditch the automated app.config approach) - then you have complete control over when and where it is loaded and saved.

But, fundamentally, there's a big code smell and I'd want to know why the standard xml configuration approach isn't working in my app when it works fine in thousands of others.