iot/projects/Infrastructure/Office/NPOIExtensions.cs

using NPOI.SS.UserModel;
using System;
using System.Collections.Generic;

namespace Infrastructure.Office
{
    public static class NPOIExtensions
    {
        public static IEnumerable<ISheet> GetSheets(this IWorkbook wookbook)
        {
            if (wookbook is null)
            {
                throw new ArgumentNullException(nameof(wookbook));
            }

            for (int i = 0; i < wookbook.NumberOfSheets; i++)
            {
                yield return wookbook.GetSheetAt(i);
            }
        }

        public static IEnumerable<IRow> GetRows(this ISheet sheet)
        {
            if (sheet is null)
            {
                throw new ArgumentNullException(nameof(sheet));
            }
            for (int i = 0; i < sheet.LastRowNum; i++)
            {
                yield return sheet.GetRow(i);
            }
        }

        public static IEnumerable<ICell> GetCells(this IRow row)
        {
            if (row is null)
            {
                throw new ArgumentNullException(nameof(row));
            }
            for (int i = 0; i < row.LastCellNum; i++)
            {
                yield return row.GetCell(i);
            }
        }

        public static object GetValue(this ICell cell)
        {
            if (cell is null)
            {
                throw new ArgumentNullException(nameof(cell));
            }
            object result = cell.CellType switch
            {
                CellType.Unknown => cell.ToString().Trim(),
                CellType.Numeric => cell.NumericCellValue,
                CellType.String => cell.StringCellValue.Trim(),
                CellType.Formula => cell.CellFormula,
                CellType.Blank => null,
                CellType.Boolean => cell.BooleanCellValue,
                CellType.Error => cell.ErrorCellValue,
                _ => cell.ToString().Trim(),
            };
            return result;
        }
    }
}