C# EXCEL 테이블을 DataTable로 변환

 private DataTable FileToDataTable(string fileName)
    {
        DataTable dt = new DataTable();
        string extendName = Path.GetExtension(fileName);// 
        switch (extendName.ToLower())
        {
            case ".xls":
                dt = XlsToDataTable(fileName);
                break;
            case ".xlsx":
                dt = XlsxToDataTable(fileName);
                break;
            default:
                break;
        }
        return dt;
    }

 private DataTable XlsToDataTable(string fileName)
    {
        DataTable dataTable = new DataTable();
        Stream stream = null;
        try
        {
            stream = File.OpenRead(fileName);
            HSSFWorkbook hssfworkbook = new HSSFWorkbook(stream);
            HSSFSheet hssfsheet = (HSSFSheet)hssfworkbook.GetSheetAt(hssfworkbook.ActiveSheetIndex);
            HSSFRow hssfrow = (HSSFRow)hssfsheet.GetRow(0);
            int lastCellNum = (int)hssfrow.LastCellNum;
            for (int i = (int)hssfrow.FirstCellNum; i < lastCellNum; i++)
            {
                DataColumn column = new DataColumn(hssfrow.GetCell(i).StringCellValue);
                dataTable.Columns.Add(column);
            }
            dataTable.TableName = hssfsheet.SheetName;
            int lastRowNum = hssfsheet.LastRowNum;
            // , TABLE 
            for (int i = hssfsheet.FirstRowNum + 1; i < hssfsheet.LastRowNum; i++)//
            {
                HSSFRow hssfrow2 = (HSSFRow)hssfsheet.GetRow(i);
                DataRow dataRow = dataTable.NewRow();
                for (int j = (int)hssfrow2.FirstCellNum; j < lastCellNum; j++)//
                {
                    dataRow[j] = hssfrow2.GetCell(j);//
                }
                dataTable.Rows.Add(dataRow);
            }
            stream.Close();
        }
        catch (Exception ex)
        {
            ScriptManager.RegisterStartupScript(Page, GetType(), "alertForm", "alert(' Xls to DataTable: " + ex.Message + "');", true);
        }
        finally
        {
            if (stream != null)
            {
                stream.Close();
            }
        }
        return dataTable;
    }

public DataTable XlsxToDataTable(string vFilePath)
    {
        DataTable dataTable = new DataTable();
        try
        {
            SLDocument sldocument = new SLDocument(vFilePath);
            dataTable.TableName = sldocument.GetSheetNames()[0];
            SLWorksheetStatistics worksheetStatistics = sldocument.GetWorksheetStatistics();
            int startColumnIndex = worksheetStatistics.StartColumnIndex;
            int endColumnIndex = worksheetStatistics.EndColumnIndex;
            int startRowIndex = worksheetStatistics.StartRowIndex;
            int endRowIndex = worksheetStatistics.EndRowIndex;
            for (int i = startColumnIndex; i <= endColumnIndex; i++)
            {
                SLRstType cellValueAsRstType = sldocument.GetCellValueAsRstType(1, i);
                dataTable.Columns.Add(new DataColumn(cellValueAsRstType.GetText(), typeof(string)));
            }
            for (int j = startRowIndex + 1; j <= endRowIndex; j++)
            {
                DataRow dataRow = dataTable.NewRow();
                for (int i = startColumnIndex; i <= endColumnIndex; i++)
                {
                    dataRow[i - 1] = sldocument.GetCellValueAsString(j, i);
                }
                dataTable.Rows.Add(dataRow);
            }
        }
        catch (Exception ex)
        {
            throw new Exception("Xlsx to DataTable: 
" + ex.Message);
        }
        return dataTable;
    }