//filePath 為儲存到本地磁碟的位置
 private void Export(string filePath)   
        {
            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
                {
                    col_txt += item.ToString() + ","; // 迴圈得到列名
                }
                col_txt = col_txt.Substring(0, col_txt.Length - 1);
                sw.WriteLine(col_txt);  <span style="white-space:pre">//寫入檔案

                foreach (DataRow item in dt.Rows)  
                {
                    row_txt = "";  <span style="white-space:pre">//此處容易遺漏，導致資料的重複新增
                    for (int i = 0; i < dt.Columns.Count; i++)  
                    {
                        row_txt += item[i].ToString() + ","; //迴圈得到行資料
                    }
                    row_txt = row_txt.Substring(0, row_txt.Length - 1);
                    sw.WriteLine(row_txt);//寫入檔案
                }
                sw.Flush();   <span style="white-space:pre">//提交所進行的操作
            }
        }