C# 使用NPOI 操作Excel

首先 Nuget 引入NPOI

一、读取Excel

/// <summary>
        /// 读取Excel数据
        /// </summary>
        public static void ReadExcel()
        {
            OpenFileDialog ofd = new OpenFileDialog();
            ofd.Filter = "Excel|*.xlsx;*.xls";
            if (ofd.ShowDialog() == DialogResult.OK)
            {
                IWorkbook workbook = null;
                //打开选择的Excel文件
                using (FileStream file = new FileStream(ofd.FileName, FileMode.Open, FileAccess.Read))
                {
                    //根据现有的Excel文档创建工作簿
                    workbook = WorkbookFactory.Create(ofd.FileName);
                }
                //获得工作表
                ISheet sheet0 = workbook.GetSheetAt();
                //获得所有行的集合
                System.Collections.IEnumerator rows = sheet0.GetRowEnumerator();
                var cellCount = sheet0.GetRow().LastCellNum;//第一行列数
                //从第一行开始读取
                for (int i = sheet0.FirstRowNum ; i <= sheet0.LastRowNum; i++)
                {
                    IRow row = sheet0.GetRow(i);
                    var cell0 = row.GetCell().ToString();//第 i 行第1列
                    var cell1 = row.GetCell().ToString();//第 i 行第2列

                    //todo something:
                }
            }
        }

二、导出到Excel

/// <summary>
        /// Datable导出成Excel
        /// </summary>
        /// <param name="dt"></param>
        /// <param name="file">导出路径(包括文件名与扩展名)</param>
        public static void TableToExcel(DataTable dt, string file)
        {
            IWorkbook workbook;
            string fileExt = Path.GetExtension(file).ToLower();
            if (fileExt == ".xlsx") { workbook = new XSSFWorkbook(); } else if (fileExt == ".xls") { workbook = new HSSFWorkbook(); } else { workbook = null; }
            if (workbook == null) { return; }
            ISheet sheet = string.IsNullOrEmpty(dt.TableName) ? workbook.CreateSheet("Sheet1") : workbook.CreateSheet(dt.TableName);

            //表头
            IRow row = sheet.CreateRow();
            for (int i = ; i < dt.Columns.Count; i++)
            {
                ICell cell = row.CreateCell(i);
                cell.SetCellValue(dt.Columns[i].ColumnName);
            }

            //数据
            for (int i = ; i < dt.Rows.Count; i++)
            {
                IRow row1 = sheet.CreateRow(i + );
                for (int j = ; j < dt.Columns.Count; j++)
                {
                    ICell cell = row1.CreateCell(j);
                    cell.SetCellValue(dt.Rows[i][j].ToString());
                }
            }

            //转为字节数组
            MemoryStream stream = new MemoryStream();
            workbook.Write(stream);
            var buf = stream.ToArray();

            //保存为Excel文件
            using (FileStream fs = new FileStream(file, FileMode.Create, FileAccess.Write))
            {
                fs.Write(buf, , buf.Length);
                fs.Flush();
            }
        }