把错误写到日志

public static void WriteLog(string strLog)
  {

   string strPath;
   strPath=System.Environment.SystemDirectory;
   strPath+=@"\ReceiveMailTimeInterval.txt";

   FileStream fs = new FileStream(strPath,FileMode.OpenOrCreate,FileAccess.Write);
   StreamWriter m_streamWriter = new StreamWriter(fs);
   m_streamWriter.BaseStream.Seek(0, SeekOrigin.End);
   m_streamWriter.WriteLine(strLog);                       
   m_streamWriter.Flush();
   m_streamWriter.Close();
   fs.Close();
  }