請問一下..為何我list保存再for裡面看的到..再寫進去..去開該csv卻是空白檔??

private void button1_Click(object sender, EventArgs e)
        {
            DateTime CurrTime = DateTime.Now;
            string year = CurrTime.Year.ToString();
            string month = CurrTime.Date.Month.ToString();
            string day = CurrTime.Date.Day.ToString();
            string path = "D:\\CVP_System\\"+year+"_"+month+".csv";
            ArrayList list = new ArrayList();
            string[] s1 = new string[31];
            string[] s2 = new string[3];
            string[] s3 = new string[2];
            int i = 0;
            if (File.Exists(path))
            {
                sr = new StreamReader(path);
                while (!sr.EndOfStream)
                {
                    list.Add(sr.ReadLine());
                }
                sr.Close();
                int x=list.Count;
                s2 = list[x-1].ToString().Split('_');
                s3=s2[1].Split(',');
                //MessageBox.Show(s3[0].Equals(day).ToString());
                if (s3[0] == day) 
                {
                    StreamWriter sw = new StreamWriter(path);
                    for(int z = 0; z < x; z++) 
                    {
                        sw.WriteLine(list[z].ToString());
                    }
                }
            }
        }

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