利用NPOI将Excel数据转DataTable

        /// <summary>
        /// 将Excel数据转换成DataTable
        /// </summary>
        /// <param name="xlsxFile"></param>
        /// <returns></returns>
        private List<DataTable> GetDataTablesFromExcel(string xlsxFile)
        {
            if (!File.Exists(xlsxFile))
                throw new FileNotFoundException("文件不存在");
            List<DataTable> dataTableList = new List<DataTable>();
            using (FileStream fileStream = new FileStream(xlsxFile, FileMode.Open, FileAccess.Read))
            {
                IWorkbook workbook = !(Path.GetExtension(xlsxFile) == ".xlsx") ? (IWorkbook)new HSSFWorkbook((Stream)fileStream) : (IWorkbook)new XSSFWorkbook((Stream)fileStream);
                for (int index = 0; index < workbook.NumberOfSheets; index++)
                {
                    DataTable dataTable = new DataTable();
                    ISheet sheetAt = workbook.GetSheetAt(index);
                    if (sheetAt==null)
                    {
                        continue;
                    }
                    dataTable.TableName = sheetAt.SheetName;
                    int rowsCount = sheetAt.PhysicalNumberOfRows;//获取Excel的最大行数
                    if (rowsCount <= 1) continue;
                    //为保证Table布局与Excel一样，这里应该取所有行中的最大列数（需要遍历整个Sheet）。
                    //为少一交全Excel遍历，提高性能，我们可以人为把第0行的列数调整至所有行中的最大列数。
                    int colsCount = sheetAt.GetRow(0).PhysicalNumberOfCells;

                    //取表格第一行（标题）为Columns
                    for (int i = 0; i < colsCount; i++)
                    {
                        var cellValue = sheetAt.GetRow(0).GetCell(i);
                        dataTable.Columns.Add(cellValue?.ToString());
                    }

                    //从第二行取数据，第一行默认为标题
                    for (int x = 1; x < rowsCount; x++)
                    {
                        DataRow dr = dataTable.NewRow();
                        for (int y = 0; y < colsCount; y++)
                        {
                            var cellValue = sheetAt.GetRow(x).GetCell(y);
                            dr[y] = cellValue?.ToString();
                        }
                        dataTable.Rows.Add(dr);
                    }
                    dataTableList.Add(dataTable);
                }
            }
            return dataTableList;
        }