b5c5aa20_e_log4net_Manual__Introduction__Description
[Type] log4net.Appender.OutputDebugStringAppender [Description] 
Writes logging events to the debugger. If the application has no debugger, the system debugger displays the string. If the application has no debugger and the system debugger is not active, the message is ignored.
Apache log4net – Apache log4net Manual: Introduction
Description