excel 파일이 DataTable로 변환

#region excel datatable
        /// 

        ///  excel DataTable 
        /// 
        ///  DataTable 
        ///  
        /// excel sheet 
        ///  DataTable
        public static DataTable ExcelToDataTable(bool isFirstRowColumn, string fileName, string sheetName = "")
        {
            if (string.IsNullOrEmpty(fileName))
            {
                throw new ArgumentNullException(fileName);
            }
            var data = new DataTable();
            IWorkbook workbook = null;
            FileStream fs = null;
            try
            {
                fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
                if (fileName.IndexOf(".xlsx", StringComparison.Ordinal) > 0)
                {
                    workbook = new XSSFWorkbook(fs);
                }
                if (fileName.IndexOf(".xls", StringComparison.Ordinal) > 0)
                {
                    workbook = new HSSFWorkbook(fs);
                }

                ISheet sheet = null;
                if (workbook != null)
                {
                    // sheetName sheet， sheet
                    if (sheetName == "")
                    {
                        sheet = workbook.GetSheetAt(0);
                    }
                    else
                    {
                        sheet = workbook.GetSheet(sheetName) ?? workbook.GetSheetAt(0);
                    }
                }
                if (sheet == null) return data;
                var firstRow = sheet.GetRow(0);
                // cell   
                int cellCount = firstRow.LastCellNum;
                int startRow;
                if (isFirstRowColumn)
                {
                    for (int i = firstRow.FirstCellNum; i < cellCount; ++i)
                    {
                        var cell = firstRow.GetCell(i);
                        var cellValue = cell.StringCellValue;
                        if (cellValue == null) continue;
                        var column = new DataColumn(cellValue);
                        data.Columns.Add(column);
                    }
                    startRow = sheet.FirstRowNum + 1;
                }
                else
                {
                    startRow = sheet.FirstRowNum;
                }
                // 
                var rowCount = sheet.LastRowNum;
                for (var i = startRow; i <= rowCount; ++i)
                {
                    var row = sheet.GetRow(i);
                    // null
                    if (row == null) continue;
                    var dataRow = data.NewRow();
                    for (int j = row.FirstCellNum; j < cellCount; ++j)
                    {
                        // ， null
                        if (row.GetCell(j) != null)
                            dataRow[j] = row.GetCell(j).ToString();
                    }
                    data.Rows.Add(dataRow);
                }

                return data;
            }
            catch (IOException ioex)
            {
                throw new IOException(ioex.Message);
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }
            finally
            {
                if (fs != null)
                {
                    fs.Close();
                }
            }
        }
        #endregion