log4net (common.logging) erroneous exception

Question

I have the following log4net statement in a c# application:

log.Info(CultureInfo.InvariantCulture, m => m(notice));

with the string contents of:

notice = "Checking: 645: Bp $B!!:{4V7r;K Bp $B$D$^$M$5$S (B <xxx@xxxxxx. Co. Jp> (B <xxxxx@xxxxxxx.Com>)"

causing this exception:

[Common.Logging.Factory.AbstractLogger+FormatMessageCallbackFormattedMessage]System.FormatException: Index (zero based) must be greater than or equal to zero and less than the size of the argument list. at System.Text.StringBuilder.AppendFormat(IFormatProvider provider, String format, Object[] args) at System.String.Format(IFormatProvider provider, String format, Object[] args) at Common.Logging.Factory.AbstractLogger.FormatMessageCallbackFormattedMessage.FormatMessage(String format, Object[] args)

If you notice in the string (which, in this case, is a totally piece of garbage) there is a single bracket "{". I'm fairly certain that this is causing the exception. What can I do to avoid this? Escape the string somehow?

It's a fairly harmless exception, except that it shows up in the log file and is distracting.

Answer 1

It ends up that the Common.Logging log function uses the string.Format functions regardless of whether they are needed or not. So, as @HansKesting mentioned in comments, escaping any unintended brackets (braces) will be needed. So, when logging data that I suspect my have this problem, I changed the code to:

notice = notice.Replace("{", "{{");
log.Info(CultureInfo.InvariantCulture, m => m(notice));

Hopes this helps others.

Answer 2

You are using a self writen extention which accepts a Action as log argument. Your method m(string) causes an error. You should check the source code of your method m. Log4net it self will never cause any errors because it is designed to fail silent. If the error is caused by log4net you would have find a critical bug.

The reason log4net does not accept a Action<string> as argument is that it can have side affects like this.