c# - Writing stack trace to log file only when exception thrown -

i want write stack trace when have exceptions,

 layout="${longdate}|${level}|${message} ${exception:format=tostring} | ${stacktrace}" 

so in log file.

edit:

i use layout logging, when dont have exceptions stack trace.but need when have exception

when have exception have following output, , need

2011-07-01 22:59:02.3782|debug|fffffffffffffffffffffffffffff system.exception: exception of type 'system.exception' thrown. | appdomain.executeassembly => appdomain._nexecuteassembly => program.main 

but without exception :

2011-07-01 22:57:26.7117|trace|fffffffffffffffffffffffffffff  | appdomain.executeassembly => appdomain._nexecuteassembly => program.main 

but want only

2011-07-01 22:57:26.7117|trace|fffffffffffffffffffffffffffff 

need ideas how so...

yes, in nlog can use different levels warn, error info etc. can log exceptions errorexception, warnexception, infoexception. ie

logger.error("this error message"); 

if want show exception use following.

logger.errorexception("this error exception", e); 

update :

<target name="errors" xsi:type="file" filename="${logdirectory}/errorlog.txt" layout="${longdate} ${message} ${exception:format=tostring}"/> 

remove {stacktrace}

update :

exception e = new exception(); e.stacktrace // <= exception holds stack trace 

you stacktrace exception.