class Log
    {
        public static void Save(string message)
        {
            using (System.IO.StreamWriter sw = new System.IO.StreamWriter("" + AppDomain.CurrentDomain.BaseDirectory + "\\log.txt", true))
            {
                sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + "\t" + message+ "\r");
                sw.Flush();
                sw.Close();  //数据写入log.txt
            }                  
                
        }

    }

AppDomain.CurrentDomain.BaseDirectory