static void FileStreamSDemo()
        {
            DateTime dtNow = DateTime.Now;
            DateTime dtEnd = dtNow.AddSeconds(60);
            using(FileStream fs=new FileStream("FileStream.txt",FileMode.Create))
            {
                while (DateTime.Now < dtEnd)
                {
                    string msg = $"Now is {DateTime.Now.ToString("yyyyMMddHHmmssffff")},Guid is {Guid.NewGuid()}";
                    byte[] data = Encoding.UTF8.GetBytes(msg);
                    fs.Write(data, 0, data.Length);
                }
            }           
        }

        static void StreamWriterDemo()
        {
            DateTime dtNow = DateTime.Now;
            DateTime dtEnd = dtNow.AddSeconds(60);
            using(StreamWriter writer=new StreamWriter("StreamWriter.txt",true,Encoding.UTF8))
            {
                while(DateTime.Now<dtEnd)
                {
                    string msg = $"Now is {DateTime.Now.ToString("yyyyMMddHHmmssffff")},Guid is {Guid.NewGuid()}";
                    writer.WriteLine(msg);
                }
            }
        }