MaxSizeRollBackups can not works

when set the <PreserveLogFileNameExtension value="true" /> ,the <MaxSizeRollBackups value="2"/> can not works. The issus is caused by func. RollingFileAppender:RollOverRenameFiles(string baseFileName) and I changed to this. protected void RollOverSize() { this.CloseFile(); // keep windows happy. LogLog.Debug(declaringType, "rolling over count ["+((CountingQuietTextWriter)QuietWriter).Count+"]"); LogLog.Debug(declaringType, "maxSizeRollBackups ["+m_maxSizeRollBackups+"]"); LogLog.Debug(declaringType, "curSizeRollBackups ["+m_curSizeRollBackups+"]"); LogLog.Debug(declaringType, "countDirection ["+m_countDirection+"]"); RollOverRenameFiles(File); //if (!m_staticLogFileName && m_countDirection >= 0) //{ // m_curSizeRollBackups++; //} // This will also close the file. This is OK since multiple close operations are safe. SafeOpenFile(m_baseFileName, false); } protected void RollOverRenameFiles(string baseFileName) { // If maxBackups <= 0, then there is no file renaming to be done. if (m_maxSizeRollBackups != 0) { if (m_countDirection < 0) { // Delete the oldest file, to keep Windows happy. if (m_curSizeRollBackups == m_maxSizeRollBackups) {                         DeleteFile(CombinePath(baseFileName, "." + m_maxSizeRollBackups)); m_curSizeRollBackups--; } // Map {(maxBackupIndex - 1), ..., 2, 1} to {maxBackupIndex, ..., 3, 2} for (int i = m_curSizeRollBackups; i >= 1; i--) {                         RollFile((CombinePath(baseFileName, "." + i)), (CombinePath(baseFileName, "." + (i + 1)))); } m_curSizeRollBackups++; // Rename fileName to fileName.1                     RollFile(baseFileName, CombinePath(baseFileName, ".1")); } else {                     //countDirection >= 0                     if (m_curSizeRollBackups >= m_maxSizeRollBackups && m_maxSizeRollBackups > 0)                     {                                                  if (!m_preserveLogFileNameExtension)                         {                             //delete the first and keep counting up.                             int oldestFileIndex = m_curSizeRollBackups - m_maxSizeRollBackups;                             // If static then there is 1 file without a number, therefore 1 less archive                             oldestFileIndex++;                             // If using a static log file then the base for the numbered sequence is the baseFileName passed in                             // If not using a static log file then the baseFileName will already have a numbered postfix which                             // we must remove, however it may have a date postfix which we must keep!                             string archiveFileBaseName = baseFileName;                             if (!m_staticLogFileName)                             {                                 int lastDotIndex = archiveFileBaseName.LastIndexOf(".");                                 if (lastDotIndex >= 0)                                 {                                     archiveFileBaseName = archiveFileBaseName.Substring(0, lastDotIndex);                                 }                             }                             // Delete the archive file                             DeleteFile(CombinePath(archiveFileBaseName, "." + oldestFileIndex));                             if (m_staticLogFileName)                             {                                 m_curSizeRollBackups++;                                 RollFile(baseFileName, CombinePath(baseFileName, "." + m_curSizeRollBackups));                             }                         }                         else                         {                             m_curSizeRollBackups = 0;                         }                     }                     else                     {                         m_curSizeRollBackups++;                         if (m_staticLogFileName)                         {                             RollFile(baseFileName, CombinePath(baseFileName, "." + m_curSizeRollBackups));                         }                     }                 } } }