private void Export(string filePath)  //filePath為儲存到本地磁碟的位置
        {
            using (FileStream fs=new FileStream(filePath,FileMode.Create,FileAccess.Write))
            {
                StreamWriter sw = new StreamWriter(fs);

                string col_txt = "";
                string row_txt = "";

                foreach (DataColumn item in dt.Columns)  // dt  為DataTable  迴圈寫入列標題
                {
                    col_txt += item.ToString() + ",";
                }
                col_txt = col_txt.Substring(0, col_txt.Length - 1);  //去掉最後多於的逗號
                sw.WriteLine(col_txt);<span style="white-space:pre">//寫入更改

                foreach (DataRow item in dt.Rows)//迴圈寫入行資料

                {
                    row_txt = "";<span style="white-space:pre">//容易漏寫，造成資料的重複寫入
                    for (int i = 0; i < dt.Columns.Count; i++)
                    {
                        row_txt += item[i].ToString() + ",";
                    }
                    row_txt = row_txt.Substring(0, row_txt.Length - 1); //去掉最後多於的逗號

                    sw.WriteLine(row_txt);//寫入更改
                }
                sw.Flush();   //此處必須有此操作
            }
        }