Question

I am into the development of a core dll where I have a class library.I want to use log4net to enable logging for exceptions. I have an app.config file in the class library where i have given the settings for the log4net.However when I test the class library the log4net does’nt create logs until i add the app.config in the calling project inspite of the fact that i had added [assembly: log4net.Config.XmlConfigurator(Watch = true)] in the class libary’s assemblyinfo.cs and I am using log4net.ILog logger = log4net.LogManager.GetLogger(typeof(ErrorHandler)) where ErrorHandler is the name of my class library’s class where log4net’s calling functions are handled.Any ideas on what is going wrong?

Secondly, what I want to acheive is the users of my dll will just pass the location where they want to create logs and whether they want to create logs in event viewer or log files from their app.config? They will not handle any other setting of log4net.

Any suggestions or code snippets for the first issue and the second problem?

Answer 1

Only the “main” app.config is active for a .Net application. Your library config file is simply ignored. Either you transfer your settings to the main config file or you use an external config file for log4net. You configure it then for instance like this (assuming you call it log4net.config):

[assembly: log4net.Config.XmlConfigurator(ConfigFile = "log4net.config", Watch = true)]

Please note that the structure of the config file is a bit different:

<?xml version="1.0" encoding="utf-8" ?>
<log4net>
    <appender name="YourAppender" type="..." >
      ....
    </appender>
    <root>
        <level value="ALL" />
        <appender-ref ref="YourAppender" />
    </root>
</log4net>

As for your second problem: I am not sure how flexible this has to be. Is it just switching from file appender to event log appender? Depending on your answer you may consider two prepare to configuration files (e.g. file.log4net and eventlog.log4net) and read the configuration as needed (in that case you cannot use the attribute: you call the Configure() method directly) or if your requirements are more complex you might even end up configuring log4net programatically.