This week, an application I work on started logging an exception that provided no help at all in debugging the problem. My usual practice of running the app in debug mode with production values in the config file failed to reproduce the error too. After a couple of days of checking a bunch of different areas of code (and still not solving the problem), Bob (a consultant from Intervention Technologies) gave me some code to get at all the InnerException values for a given Exception. Download the function from here.
StackTrace can be pretty large. Since we log to a database, I was worried about overrunning the column width. I also wasn’t keen on the idea of looking at so large a text block if an Exception was nesting four or five additional ones. So instead of implementing the code above, I changed the code to log at each level. Doing it this way adds a log entry for each InnerException. Because the log viewer I implemented displays the entries in reverse-chronological order, the root cause of a really gnarly exception displays at the top. The changes I made to global.asax looked like this.
The result of this work revealed that the app had been complaining about not being able to reach the SMTP server to send e-mail (which it needs to send users their passwords when they register or recover lost passwords).
Once we’d established that the change was working properly, it was time to refactor the code to make the functionality more broadly available. To accomplish this, I updated our Log4Net wrapper like this.