使用NPOI导出导入导出Excel

Excel2003

    #region Excel2003
    /// <summary>
    /// 将Excel文件中的数据读出到DataTable中(xls)
    /// </summary>
    /// <param name="file"></param>
    /// <returns></returns>
    public static DataTable ExcelToTableForXLS(string file)
    {
        DataTable dt = new DataTable();
        using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read))
        {
            XLS.HSSFWorkbook hssfworkbook = new XLS.HSSFWorkbook(fs);
            ISheet sheet = hssfworkbook.GetSheetAt(0);

            //表头
            IRow header = sheet.GetRow(sheet.FirstRowNum);
            List<int> columns = new List<int>();
            for (int i = 0; i < header.LastCellNum; i++)
            {
                object obj = GetValueTypeForXLS(header.GetCell(i) as XLS.HSSFCell);
                if (obj == null || obj.ToString() == string.Empty)
                {
                    dt.Columns.Add(new DataColumn("Columns" + i.ToString()));
                    //continue;
                }
                else
                    dt.Columns.Add(new DataColumn(obj.ToString()));
                columns.Add(i);
            }
            //数据
            for (int i = sheet.FirstRowNum + 1; i <= sheet.LastRowNum; i++)
            {
                DataRow dr = dt.NewRow();
                bool hasValue = false;
                foreach (int j in columns)
                {
                    dr[j] = GetValueTypeForXLS(sheet.GetRow(i).GetCell(j) as XLS.HSSFCell);
                    if (dr[j] != null && dr[j].ToString() != string.Empty)
                    {
                        hasValue = true;
                    }
                }
                if (hasValue)
                {
                    dt.Rows.Add(dr);
                }
            }
        }
        return dt;
    }

    /// <summary>
    /// 将DataTable数据导出到Excel文件中(xls)
    /// </summary>
    /// <param name="dt"></param>
    /// <param name="file"></param>
    public static void TableToExcelForXLS(DataTable dt, string file)
    {
        XLS.HSSFWorkbook hssfworkbook = new XLS.HSSFWorkbook();
        ISheet sheet = hssfworkbook.CreateSheet("Test");

        //表头
        IRow row = sheet.CreateRow(0);
        for (int i = 0; i < dt.Columns.Count; i++)
        {
            ICell cell = row.CreateCell(i);
            cell.SetCellValue(dt.Columns[i].ColumnName);
        }

        //数据
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            IRow row1 = sheet.CreateRow(i + 1);
            for (int j = 0; 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();
        hssfworkbook.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, 0, buf.Length);
            fs.Flush();
        }
    }

    /// <summary>
    /// 获取单元格类型(xls)
    /// </summary>
    /// <param name="cell"></param>
    /// <returns></returns>
    private static object GetValueTypeForXLS(XLS.HSSFCell cell)
    {
        if (cell == null)
            return null;
        switch (cell.CellType)
        {
            case CellType.BLANK: //BLANK:
                return null;
            case CellType.BOOLEAN: //BOOLEAN:
                return cell.BooleanCellValue;
            case CellType.NUMERIC: //NUMERIC:
                return cell.NumericCellValue;
            case CellType.STRING: //STRING:
                return cell.StringCellValue;
            case CellType.ERROR: //ERROR:
                return cell.ErrorCellValue;
            case CellType.FORMULA: //FORMULA:
            default:
                return "=" + cell.CellFormula;
        }
    }
    #endregion

Excel2007

    #region Excel2007
    /// <summary>
    /// 将Excel文件中的数据读出到DataTable中(xlsx)
    /// </summary>
    /// <param name="file"></param>
    /// <returns></returns>
    public static DataTable ExcelToTableForXLSX(string file)
    {
        DataTable dt = new DataTable();
        using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read))
        {
            XSSFWorkbook xssfworkbook = new XSSFWorkbook(fs);
            ISheet sheet = xssfworkbook.GetSheetAt(0);

            //表头
            IRow header = sheet.GetRow(sheet.FirstRowNum);
            List<int> columns = new List<int>();
            for (int i = 0; i < header.LastCellNum; i++)
            {
                object obj = GetValueTypeForXLSX(header.GetCell(i) as XSSFCell);
                if (obj == null || obj.ToString() == string.Empty)
                {
                    dt.Columns.Add(new DataColumn("Columns" + i.ToString()));
                    //continue;
                }
                else
                    dt.Columns.Add(new DataColumn(obj.ToString()));
                columns.Add(i);
            }
            //数据
            for (int i = sheet.FirstRowNum + 1; i <= sheet.LastRowNum; i++)
            {
                DataRow dr = dt.NewRow();
                bool hasValue = false;
                foreach (int j in columns)
                {
                    dr[j] = GetValueTypeForXLSX(sheet.GetRow(i).GetCell(j) as XSSFCell);
                    if (dr[j] != null && dr[j].ToString() != string.Empty)
                    {
                        hasValue = true;
                    }
                }
                if (hasValue)
                {
                    dt.Rows.Add(dr);
                }
            }
        }
        return dt;
    }

    /// <summary>
    /// 将DataTable数据导出到Excel文件中(xlsx)
    /// </summary>
    /// <param name="dt"></param>
    /// <param name="file"></param>
    public static void TableToExcelForXLSX(DataTable dt, string file)
    {
        XSSFWorkbook xssfworkbook = new XSSFWorkbook();
        ISheet sheet = xssfworkbook.CreateSheet("Test");

        //表头
        IRow row = sheet.CreateRow(0);
        for (int i = 0; i < dt.Columns.Count; i++)
        {
            ICell cell = row.CreateCell(i);
            cell.SetCellValue(dt.Columns[i].ColumnName);
        }

        //数据
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            IRow row1 = sheet.CreateRow(i + 1);
            for (int j = 0; j < dt.Columns.Count; j++)
            {
                ICell cell = row1.CreateCell(j);
                cell.SetCellValue(dt.Rows[i][j].ToString());
            }
        }
            /*不能使用如下方法生成Excel，因为在xssfworkbook.Write(stream);操作后会关闭流，导致报错【不能操作已关闭的流】*/
            ////转为字节数组
            //MemoryStream stream = new MemoryStream();
            //xssfworkbook.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, 0, buf.Length);
            //    fs.Flush();
            //}
            /*可以使用下面方式导出*/
            MemoryStream stream = new MemoryStream();
            xssfworkbook.Write(stream);
            Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";//经过测试发现不添加会打不开excel本地可以
            Response.AddHeader("Content-Disposition", string.Format("attachment; filename={0}.xlsx", DateTime.Now.ToString("yyyyMMddHHmmssfff")));
            Response.BinaryWrite(stream.ToArray());
            xssfworkbook = null;
            stream.Close();
            stream.Dispose();
    }

    /// <summary>
    /// 获取单元格类型(xlsx)
    /// </summary>
    /// <param name="cell"></param>
    /// <returns></returns>
    private static object GetValueTypeForXLSX(XSSFCell cell)
    {
        if (cell == null)
            return null;
        switch (cell.CellType)
        {
            case CellType.BLANK: //BLANK:
                return null;
            case CellType.BOOLEAN: //BOOLEAN:
                return cell.BooleanCellValue;
            case CellType.NUMERIC: //NUMERIC:
                return cell.NumericCellValue;
            case CellType.STRING: //STRING:
                return cell.StringCellValue;
            case CellType.ERROR: //ERROR:
                return cell.ErrorCellValue;
            case CellType.FORMULA: //FORMULA:
            default:
                return "=" + cell.CellFormula;
        }
    }            

注意：上文提到使用NPOI导出excel2007的时候会报错【不能操作已经关闭的流】，原因是在write的时候给Dispose了，故可以重写MemenryStream的Dispose接口，代码如下：

　　 /// <summary>
    /// 这是为了避免流被NPOI关闭而实现的流
    /// 当CanDispose为false时此流的dispose接口无效，仅当该值为true时有效
    /// </summary>
    public class ExcelStream:System.IO.MemoryStream
    {
        protected override void Dispose(bool disposing)
        {
            if (CanDispose)
            {
                base.Dispose(disposing);
            }
        }

        public bool CanDispose { get; set; }
    }

如下调用：

　　　　ExcelStream stream = new ExcelStream();
       workbook.Write(stream);
       stream.CanDispose = true;

注意：操作Excel2003与操作Excel2007使用的是不同的命名空间下的内容

使用NPOI.HSSF.UserModel空间下的HSSFWorkbook操作Excel2003

使用NPOI.XSSF.UserModel空间下的XSSFWorkbook操作Excel2007

感谢：http://blog.csdn.net/halym/article/details/9235823

感谢：http://www.cnblogs.com/yu-er/p/3434173.html