Gets or sets a value indicating whether to preserve the file name extension when rolling.
true if the file name extension should be preserved.
By default file.log is rolled to file.log.yyyy-MM-dd or file.log.curSizeRollBackup. However, under Windows the new file name will loose any program associations as the extension is changed. Optionally file.log can be renamed to file.yyyy-MM-dd.log or file.curSizeRollBackup.log to maintain any program associations.
RollingFileAppender Class | log4net.Appender Namespace