方法没有采用“2”个参数的重载

主要问两个问题，一个是“方法没有采用“2”个参数的重载”下面有说明错误在哪里
一个是怎么输出二维表到Excel中

封转了一个方法

/// <summary>   

    /// 由DataSet导出Excel    

    /// </summary>    

    /// <param name="sourceTable">要导出数据的DataTable</param>    

    /// <param name="sheetName">工作表名称</param>    

    /// <returns>Excel工作表</returns>    

    private static Stream ExportDataSetToExcel(DataSet sourceDs, string sheetName)    

    {

        HSSFWorkbook workbook = new HSSFWorkbook();

        MemoryStream ms = new MemoryStream();

        string [] sheetNames = sheetName.Split(',');

        for(int i = 0;i< sheetNames.Length; i++)

        {

            HSSFSheet sheet = workbook.CreateSheet(sheetNames[i]);

            HSSFRow headerRow = sheet.CreateRow(0);

            // handling header

            foreach (DataColumn column in sourceDs.Tables[i].Columns)

                headerRow.CreateCell(column.Ordinal).SetCellValue(column.ColumnName);

            // handling value.

            int rowIndex = 1;

            foreach (DataRow row in sourceDs.Tables[i].Rows)

            {

                HSSFRow dataRow = sheet.CreateRow(rowIndex);

                foreach (DataColumn column in sourceDs.Tables[i].Columns)

                {

                    dataRow.CreateCell(column.Ordinal).SetCellValue(row[column].ToString());

                }

                rowIndex++;

            }

        }

        workbook.Write(ms);

        ms.Flush();

        ms.Position = 0;

        workbook = null;

        return ms;

    }

    /// <summary>

    /// 由DataSet导出Excel

    /// </summary>

    /// <param name="sourceTable">要导出数据的DataTable</param>

    /// <param name="fileName">指定Excel工作表名称</param>

    /// <returns>Excel工作表</returns>

    public static void ExportDataSetToExcel(DataSet sourceDs, string fileName, string sheetName)

    {

        MemoryStream ms = ExportDataSetToExcel(sourceDs, sheetName) as MemoryStream;

        HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" + fileName);

        HttpContext.Current.Response.BinaryWrite(ms.ToArray());

        HttpContext.Current.Response.End();

        ms.Close();

        ms = null;

    }

页面方法调用：
DataSet ds = ExcelHelper.ExportDataSetToExcel(CommandType.Text, purchasebll.GetList(sSql2));
这句就报错了,ExportDataSetToExcel”方法没有采用“2”个参数的重载，其实我不用这句也能打印出来数据，我就是像弄明白这个是干什么的

//导出Excel

    protected void OutputExcel_Click(object sender, EventArgs e)

    {

        //DataSet ds = purchasebll.GetList1(sSql2);

        DataSet ds = ExcelHelper.ExportDataSetToExcel(CommandType.Text, purchasebll.GetList(sSql2));//这句报错，ExportDataSetToExcel”方法没有采用“2”个参数的重载

        string filename = "stock.xls";

        ExcelHelper.ExportDataSetToExcel(ds,filename,"gap");

    }

这个是输出一览表的形式输出的，挺简单的，如果是一张二维表，用什么办法输出到页面上