Activate the options on the file appender.
IOptionHandler.ActivateOptions
This is part of the IOptionHandler delayed object activation scheme. The ActivateOptions method must be called on this object after the configuration properties have been set. Until ActivateOptions is called this object is in an undefined state and must not be used.
If any of the configuration properties are modified then ActivateOptions must be called again.
This will cause the file to be opened.
FileAppender Class | log4net.Appender Namespace