public class LogHelper
{
       ...
        //实例方法
        public void WriteLog(LogType logType, string msgNumber)
        {
            ...
        }

        public static void WriteLog(LogType logType, 
            string msgNumber,
            LogTimeCycle timeCycle= LogTimeCycle.daily,
            string extraLogFileName= ""
            )
        {
           ...
        }
}