private void button8_Click(object sender, EventArgs e)
        {
            string logPath = Environment.GetFolderPath(Environment.SpecialFolder.System) + "\\" + "omidyLog";
            string logFile = logPath +"\\"+DateTime.Now.ToShortDateString()+".log";

            //在系统目录下创建日志文件夹
            if (!Directory.Exists(logPath))
            { 
                Directory.CreateDirectory(logPath);
            }

            //在日志文件夹下创建当天日期的日志文件
            if (!File.Exists(logFile))
            {
                //注意文件创建后要关闭它
                FileStream tempFS = File.Create(logFile);
                tempFS.Close();
            }

            FileStream fs = new FileStream(logFile, FileMode.Append, FileAccess.Write);
            StreamWriter sw = new StreamWriter(fs);
            sw.WriteLine(DateTime.Now.ToLongDateString() + " " + DateTime.Now.ToLongTimeString());
            sw.Close();
        }