Logging is a very important part of an application. It provides detailed information about the application workflow, even when an application is already deployed to several clients. That’s the reason that logging is a first class citizen in the Catel framework.

In general, logging works by defining an ILog instance on a class:

private static readonly ILog Log = LogManager.GetCurrentClassLogger();

Then in any method, logging can be added like this:

Log.Info(“This is a logging with a format ‘{0}’”, “test”);

Writing the Log definition can be boring and repetitive. Luckily Simon Cropp came up with a solution for that, namely Anotar.Catel.Fody. With the Anotar implementation, a reference will be added to the solution. Then after compilation the assembly will be removed and all calls to the LogTo class will be replaced by actual calls to the Catel logging classes.

How to use Anotar

Using Anotar is really easy, just call the static methods on the LogTo class as you can see below:

LogTo.Info("This is a logging with a format ‘{0}’", “test”);

Note that it is no longer required to define the Log field, it will be added automatically by Anotar.

Besides that it is really easy to use, another benefit is a very small performance improvement. The GetCurrentClassLogger uses reflection to determine the current class. This is a very slight hit on performance the first time a class is used (only once, the field is static). Anotar directly replaces the call by an implementation like this:

private static readonly ILog Log = LogManager.GetLogger(typeof(MyClass));

Additional options

Disabling method names and line numbers

By default Anotar also logs the method and line number:

03:58:11:858 => [DEBUG] [AnotarDemo.Program] Method: 'Void Main(String[])'. Line: ~19. this is a test

If you don’t want such output, add this attribute on assembly level:

[assembly: LogMinimalMessage]

Then the output will look like this:

03:59:36:344 => [DEBUG] [AnotarDemo1.Program] this is a test

Logging exceptions automatically

It is possible to automatically log exceptions inside a method. To accomplish this, decorate the method with the LogTo[LogLevel]OnException attribute:

public static void ExceptionalMethod()
    throw new Exception("This will be logged automatically");

Then the output will be as follows:

04:01:48:331 => [DEBUG] [AnotarDemo.Program] Exception occurred in 'Void ExceptionalMethod()'.  | [Exception] System.Exception: This will be logged automatically
   at AnotarDemo.Program.ExceptionalMethod() in c:\Source\AnotarDemo\AnotarDemo\Program.cs:line 27


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