public RollingLogFileAppender() {
if (!Directory.Exists(LOG_DIR))
Directory.CreateDirectory(LOG_DIR);
//get last rolled file
int lastCount = GetLastRollCount();
_currentRollCount = lastCount == 0 ? 1 : lastCount;
ClearExpiredFile();
ImmediateFlush = false;
AppendToFile = true;
File = CurrnetFileName;
}