C# 導出excel（.csv格式）

private void ExportExcel(string txtPath, string ReportPath, DataSet ds)     {         DataTable dt_header = ds.Tables[0];         string data = CSV_DT2(dt_header);         string tempfile = Server.MapPath(@"~/File/");         string txtfile = "20121583.txt";         string excelfile =  "20121583.csv";         WriteTxt(tempfile + txtfile, data);         File.Copy(tempfile + txtfile, tempfile + excelfile);         Response.Redirect(@"~/File/" + excelfile);         Response.End();     }     public string CSV_DT2(DataTable dt)     {

        StringBuilder data = new StringBuilder();

        //  寫出欄名         foreach (DataColumn column in dt.Columns)         {             data.Append(" " + column.ColumnName.TrimEnd() + ",");         }         data.Append("\r\n");

        //寫出資料

        foreach (DataRow row in dt.Rows)         {             foreach (DataColumn column in dt.Columns)             {                 data.Append(row[column].ToString().TrimEnd() + ",");             }             data.Append("\r\n");         }         data.Append("\r\n");

        string str = data.ToString();         // str = str.ToString(Encoding.UTF8);         return str;     }     public void WriteTxt(string filename, string msg)     {         if (File.Exists(filename.Trim()))         {             File.Delete(filename);         }         StreamWriter sw = new StreamWriter(filename, false, Encoding.Default);         sw.Write(msg);         sw.Close();

    }