log4net has a lot of options when it comes to defining what you write to your log. While all the patterns are documented, it is useful to see a sample output from some code. Here is the output produced from some of the patterns available:

Pattern Class ‘BaseClass’ Class ‘SubClass’
appdomain log4netPatterns.vshost.exe log4netPatterns.vshost.exe
date 2009-05-24 16:37:26,578 2009-05-24 16:37:26,640
file C:\Dev\GoogleCode-Gardiner\trunk\Log4netPatterns\log4netPatterns\Program.cs C:\Dev\GoogleCode-Gardiner\trunk\Log4netPatterns\log4netPatterns\Program.cs
location log4netPatterns.BaseClass`1.MyMethod(C:\Dev\GoogleCode-Gardiner\trunk\Log4netPatterns\log4netPatterns\Program.cs:32) log4netPatterns.SubClass.MyMethod(C:\Dev\GoogleCode-Gardiner\trunk\Log4netPatterns\log4netPatterns\Program.cs:49)
line 32 49
logger log4netPatterns.BaseClass`1[[System.Int32, mscorlib, Version=, Culture=neutral, PublicKeyToken=b77a5c561934e089]] log4netPatterns.SubClass
message BaseClass SubClass
method MyMethod MyMethod
property {log4net:HostName=morgan} {log4net:HostName=morgan}
timestamp 45968 46015
thread 2116 2116
type log4netPatterns.BaseClass`1 log4netPatterns.SubClass
username MORGAN\David MORGAN\David
utcdate 2009-05-24 07:14:41,468 2009-05-24 07:14:41,515

Of particular interest is the difference between logger and type. For the SubClass class, they result in the same output, but for the BaseClass logger is a lot more verbose (especially if your generic type happens to be from a strongly-signed assembly!). Using logger will give more detailed information but at the expense of larger log files.


Because some of the patterns vary their output if you are in a base class or an inherited class, I created a simple class hierarchy, and also included use of generics.

public class BaseClass<T>
   private ILog _log;

   public BaseClass()
       _log = LogManager.GetLogger(typeof (BaseClass<T>));

   public virtual string MyMethod(T stuff)

       return "ha";

public class SubClass : BaseClass<string>
   private ILog _log;

   public SubClass()
       _log = LogManager.GetLogger(typeof (SubClass));

   public override string MyMethod(string stuff)

       return "ho ho";

The project that included this code was strongly signed, to allow any effect this might cause to be evident.