When developing all kind of projects a good strategy for logging can save you a lot of time and frustration. Personally I am very found of using Apache log4net and this post will describe the most important features in log4net and how to implement and use this in a .Net Compact Framework project.

log4net can be configured with different appenders that logs to different sources (file, output window, smtp, server ++). You can also configure what kind of log levels will be written to the different appenders (info, debug, warn, error and fatal).

Most of the time I use two different appenders: I use the DebugAppender to log to my output window in Visual Studio, I like to set this appender to log all levels. I also like to use a LogFileAppender to log to a file on the device, I usually set this appender to only log error and fatal.

You can read documentation and download Apache log4net at http://logging.apache.org/log4net/index.html

I will show you a simple example on how to use log4net in a .Net Compact Framework project:

First you create a new Smart Device project and chose Device application. I am using Visual Studio 2008, Windows Mobile 6 professional SDK as target platform and .Net Compact Framework 3.5

The first thing you need to do after creating the project is to add the log4net.dll as a reference (log4net.dll can be downloaded from the link above).

Then you need to add a xml configuration file for log4net in your project, I added a file called Config.xml in my project and set the property to content/copy always. In this configuration file you add and setup all the different appenders and what level they will log on. You can also defined a layout pattern for the log text.

Below you can see my very simple Config.xml file containing a LogFileAppender and a DebugAppender and they are both set to log all levels.

In your Main method (by default found in Program.cs) you need to configure log4net based on the Config.xml file

log4net are now ready to be used in all classes throughout your project. For each class you want to use log4net create a static logger object in top of your class. Remember that the typeof () must be set to the class you create this logger in.

I often use the logger to log exceptions but I also use it for information and debug.

The log file on the device can be found under program files\yourProjectName\log-file.txt. This text file on the device is a very good place to for example log your global exception handling.