Problems in dynamic file naming with multiple appenders in log4net

Question

I have 3 appenders in my config file for creating 3 different types of logs. I am using dynamic naming of file in each of the 3 appenders by setting the global context properties. In some cases, i need to set the log file name dynamically for just 1 appender. When i set the file name for just 1 appender, it creates another file named "null" with no data in addition to the actual logfile whose name has been set dynamically.

<appender name="RollingFileAppenderV1" type="log4net.Appender.RollingFileAppender"> 



<file type="log4net.Util.PatternString" value="Logs\%property{applog}" /> 



. 



. 



. 



<appender name="RollingFileAppenderV2" type="log4net.Appender.RollingFileAppender"> 



<file type="log4net.Util.PatternString" value="Logs\%property{dblog}" /> 



. 



. 



<logger name="Logger1"> 



 <level value="DEBUG" /> 



 <appender-ref ref="RollingFileAppenderV1" /> 



</logger> 



<logger name="Logger2"> 



 <level value="DEBUG" /> 



 <appender-ref ref="RollingFileAppenderV2" /> 



</logger> 

In the VB.NET code i set the filename as :

log4net.GlobalContext.Properties("applog") = "file1.log" 



Dim logobj as log4net.Ilog = LogManager.GetLogger("Logger1") 



logobj.debug("test") 

In this case it creates "file1.log" and also another empty file with name as "null". This happens only when i am setting either of the appenders filename at runtime.
Any help appreciated.

Answer 1

You need to assign a value to the dblog property, which at the moment is null.

 

Either assign in code. E.g.

 

 

log4net.GlobalContextProperties("dblog") = "file2.log"

 

 

or else hard-code the name of the file (better IMHO as it overwrites the old versions of the file, preventing you from cluttering your output folder. 

So this:

 

<file type="log4net.Util.PatternString" value="Logs\%property{dblog}" />

becomes 

<file type="log4net.Util.PatternString" value="Logs\log2.log" />