how i configure log4net log.isdebugenabled true?

i am perplexing log4net an asp.net concentration visible studio 2005. i have announced an instance logger so:

private common readonly record ilog = logmanager.getlogger("")

i am perplexing following manner:

if log.isdebugenabled then
   log.debug("integration services constructed")
end if

here configuration:

<log4net>

    <root>
        <level value="debug" />
        <appender-ref ref="rollingfileappender" />
    </root>

    <appender name="rollingfileappender" type="log4net.appender.rollingfileappender">
        <file value="..\\logs\\logfile.log"/>
        <appendtofile value="true"/>
        <rollingstyle value="size"/>
        <maxsizerollbackups value="10"/>
        <maximumfilesize value="1mb"/>
        <staticlogfilename value="true"/>
        <layout type="log4net.layout.patternlayout">
            <conversionpattern value="%date [%thread] %-5level %logger [%property{ndc}] - %message%newline"/>
        </layout>
        <filter type="log4net.filter.levelrangefilter">
            <param name="levelmin" value="debug" />
            <param name="levelmax" value="fatal" />
        </filter>
    </appender>

</log4net>

unfortunately, log.isdebugenabled always false.
i configure log4net i record wholly debug messages?