1.导出

   //工作簿HSSFWorkbook

            HSSFWorkbook hssfworkbook = new HSSFWorkbook();

   //ISheet页

            ISheet sheet1 = hssfworkbook.CreateSheet("员工资料");

   //创建行         

            IRow rowHeader = sheet1.CreateRow(0);

   //设置第一行中的每一个单元格

            rowHeader.CreateCell(0, CellType.STRING).SetCellValue("工号");

   //保存

           using (Stream stream = File.OpenWrite(filename))

           {

               hssfworkbook.Write(stream);

           }

2.设置样式

           ICellStyle cellStyle = hssfworkbook.CreateCellStyle();

            IDataFormat dataFormat = hssfworkbook.CreateDataFormat();

            cellStyle.DataFormat = dataFormat.GetFormat("yyyy\"年\"m\"月\"d\"日\""); 

//入职日期

            ICell InDateCell = rowContent.CreateCell(3, CellType.NUMERIC);

            InDateCell.CellStyle = cellStyle;

            InDateCell.SetCellValue(item.InDate); 

            //设置Excel表格

3.设置宽度

在使用NPOI技术开发自动操作EXCEL软件时遇到不能精确设置列宽的问题。

如

ISheet sheet1 = hssfworkbook.CreateSheet("Sheet1");

sheet1.SetColumnWidth(0,  50 * 256);   // 在EXCEL文档中实际列宽为49.29

sheet1.SetColumnWidth(1, 100 * 256);   // 在EXCEL文档中实际列宽为99.29

sheet1.SetColumnWidth(2, 150 * 256);   // 在EXCEL文档中实际列宽为149.29

到此一般人应该知道问题出在哪了，解决方法如下:

ISheet sheet1 = hssfworkbook.CreateSheet("Sheet1");

sheet1.SetColumnWidth(0,  (int)((50 + 0.72) * 256));   // 在EXCEL文档中实际列宽为50

sheet1.SetColumnWidth(1,  (int)((100 + 0.72) * 256));   // 在EXCEL文档中实际列宽为100

sheet1.SetColumnWidth(2,  (int)((150 + 0.72) * 256));   // 在EXCEL文档中实际列宽为150

既在要设置的实际列宽中加上列宽基数：0.72

NPOI读写Excel

1、整个Excel表格叫做工作表：WorkBook（工作薄），包含的叫页（工作表）：Sheet；行：Row；单元格Cell。

2、NPOI是POI的C#版本，NPOI的行和列的index都是从0开始

3、POI读取Excel有两种格式一个是HSSF，另一个是XSSF。 HSSF和XSSF的区别如下：
HSSF is the POI Project‘s pure Java implementation of the Excel ‘97(-2007) file format.
XSSF is the POI Project‘s pure Java implementation of the Excel 2007 OOXML (.xlsx) file format.
即：HSSF适用2007以前的版本,XSSF适用2007版本及其以上的。

下面是用NPOI读写Excel的例子：ExcelHelper封装的功能主要是把DataTable中数据写入到Excel中，或者是从Excel读取数据到一个DataTable中。

ExcelHelper类：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using NPOI.SS.UserModel;using NPOI.XSSF.UserModel;using NPOI.HSSF.UserModel;using System.IO;using System.Data;namespace GMapDemo{    class ExcelHelper : IDisposable    {        private string fileName = null; //文件名        private IWorkbook workbook = null;        private FileStream fs = null;        private bool disposed;        public ExcelHelper(string fileName)        {            this.fileName = fileName;            disposed = false;        }        /// <summary>        /// 将DataTable数据导入到excel中        /// </summary>        /// <param name="data">要导入的数据</param>        /// <param name="isColumnWritten">DataTable的列名是否要导入</param>        /// <param name="sheetName">要导入的excel的sheet的名称</param>        /// <returns>导入数据行数(包含列名那一行)</returns>        public int DataTableToExcel(DataTable data, string sheetName, bool isColumnWritten)        {            int i = 0;            int j = 0;            int count = 0;            ISheet sheet = null;            fs = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.ReadWrite);            if (fileName.IndexOf(".xlsx") > 0) // 2007版本                workbook = new XSSFWorkbook();            else if (fileName.IndexOf(".xls") > 0) // 2003版本                workbook = new HSSFWorkbook();            try            {                if (workbook != null)                {                    sheet = workbook.CreateSheet(sheetName);                }                else                {                    return -1;                }                if (isColumnWritten == true) //写入DataTable的列名                {                    IRow row = sheet.CreateRow(0);                    for (j = 0; j < data.Columns.Count; ++j)                    {                        row.CreateCell(j).SetCellValue(data.Columns[j].ColumnName);                    }                    count = 1;                }                else                {                    count = 0;                }                for (i = 0; i < data.Rows.Count; ++i)                {                    IRow row = sheet.CreateRow(count);                    for (j = 0; j < data.Columns.Count; ++j)                    {                        row.CreateCell(j).SetCellValue(data.Rows[i][j].ToString());                    }                    ++count;                }                workbook.Write(fs); //写入到excel                return count;            }            catch (Exception ex)            {                Console.WriteLine("Exception: " + ex.Message);                return -1;            }        }        /// <summary>        /// 将excel中的数据导入到DataTable中        /// </summary>        /// <param name="sheetName">excel工作薄sheet的名称</param>        /// <param name="isFirstRowColumn">第一行是否是DataTable的列名</param>        /// <returns>返回的DataTable</returns>        public DataTable ExcelToDataTable(string sheetName, bool isFirstRowColumn)        {            ISheet sheet = null;            DataTable data = http://www.mamicode.com/new DataTable();".xlsx") > 0) // 2007版本                    workbook = new XSSFWorkbook(fs);                else if (fileName.IndexOf(".xls") > 0) // 2003版本                    workbook = new HSSFWorkbook(fs);                if (sheetName != null)                {                    sheet = workbook.GetSheet(sheetName);                }                else                {                    sheet = workbook.GetSheetAt(0);                }                if (sheet != null)                {                    IRow firstRow = sheet.GetRow(0);                    int cellCount = firstRow.LastCellNum; //一行最后一个cell的编号 即总的列数                    if (isFirstRowColumn)                    {                        for (int i = firstRow.FirstCellNum; i < cellCount; ++i)                        {                            DataColumn column = new DataColumn(firstRow.GetCell(i).StringCellValue);                            data.Columns.Add(column);                        }                        startRow = sheet.FirstRowNum + 1;                    }                    else                    {                        startRow = sheet.FirstRowNum;                    }                    //最后一列的标号                    int rowCount = sheet.LastRowNum;                    for (int i = startRow; i <= rowCount; ++i)                    {                        IRow row = sheet.GetRow(i);                        if (row == null) continue; //没有数据的行默认是null　　　　　　　                                                DataRow dataRow = data.NewRow();                        for (int j = row.FirstCellNum; j < cellCount; ++j)                        {                            if (row.GetCell(j) != null) //同理，没有数据的单元格都默认是null                                dataRow[j] = row.GetCell(j).ToString();                        }                        data.Rows.Add(dataRow);                    }                }                return data;            }            catch (Exception ex)            {                Console.WriteLine("Exception: " + ex.Message);                return null;            }        }        public void Dispose()        {            Dispose(true);            GC.SuppressFinalize(this);        }        protected virtual void Dispose(bool disposing)        {            if (!this.disposed)            {                if (disposing)                {                    if (fs != null)                        fs.Close();                }                fs = null;                disposed = true;            }        }    }}

【NPOI】.NET EXCEL导入导出开发包