log4net：能否将conversionPattern设为条件条件？

Question

I'm using EventLogAppender to log events from my web app to windows eventlog. Is it possible to make conversionPattern conditional so that for Error events, I can add more details?

Answer 1

I suppose you are talking about the layout capabilities of log4net; it is possible since the ILayout interface takes a LoggingEvent entity that contains the log level. I don't know however of an implementation that does that so you would have to write your own.

I think there is a simplest way though; just use two appenders, one that filters Warning and below, one that filters Error and above, and use a different layout in each appender.

<appender name="WarningAndBelowEventLogAppender" type="log4net.Appender.EventLogAppender">
    ...
    <filter type="log4net.Filter.LevelRangeFilter">
        <levelMax value="WARN" />
        <acceptOnMatch value="true" />
    </filter>
    <!-- layout for warnings and below here --> 
</appender>

<appender name="ErrorAndAboveEventLogAppender" type="log4net.Appender.EventLogAppender">
    ...
    <filter type="log4net.Filter.LevelRangeFilter">
        <levelMin value="ERROR" />
        <acceptOnMatch value="true" />
    </filter>
    <!-- layout for errors and above here --> 
</appender>

Just add the two appenders to your logging entry point (root for example) and you're done