.NET使用NPOI2.0导入导出Excel

NPOI开源地址：http://npoi.codeplex.com/

NPOI教程: http://tonyqus.sinaapp.com/

具体的不在这里写了，感兴趣的可以去官网。

先来说导出的例子

private void ExportExcel()
        {
            DataTable table_data = MAYIXUE.BLL.NPOIUtility.GetValue();

            HSSFWorkbook hssfworkbook = new HSSFWorkbook();
            ISheet sheet1 = hssfworkbook.CreateSheet("mayixue的NPOI测试1");

            ICellStyle cellStyle = hssfworkbook.CreateCellStyle();
            cellStyle.DataFormat = HSSFDataFormat.GetBuiltinFormat("0.00");
            ICellStyle stringStyle = hssfworkbook.CreateCellStyle();
            stringStyle.VerticalAlignment = VerticalAlignment.CENTER;

            //取得列宽
            int columnCount = table_data.Columns.Count;
            int[] arrColWidth = new int[columnCount];
            int width = ;
            foreach (DataColumn column in table_data.Columns)
            {
                arrColWidth[column.Ordinal] = width;
            }

            int rowIndex = ;
            string temp_col1 = "";
            int col1_s = ;

            foreach (DataRow row in table_type.Rows)
            {
                #region 新建表，填充列头，样式
                if (rowIndex ==  || rowIndex == )
                {
                    if (rowIndex != )
                    {
                        sheet1 = hssfworkbook.CreateSheet();
                    }

                    #region 列头及样式

                    IRow headerRow = sheet1.CreateRow();

                    ICellStyle headStyle = hssfworkbook.CreateCellStyle();
                    headStyle.Alignment = HorizontalAlignment.CENTER;
                    headStyle.VerticalAlignment = VerticalAlignment.CENTER;

                    IFont font = hssfworkbook.CreateFont();
                    font.FontHeightInPoints = ;
                    font.Boldweight = ;
                    headStyle.SetFont(font);

                    foreach (DataColumn column in table_type.Columns)
                    {
                        headerRow.CreateCell(column.Ordinal).SetCellValue(Convert.ToInt32(column.ColumnName));

                        headerRow.GetCell(column.Ordinal).CellStyle = headStyle;
                        sheet1.SetColumnWidth(column.Ordinal, (arrColWidth[column.Ordinal] + ) * );//设置列宽

                    }

                    #endregion

                    rowIndex = ;
                }
                #endregion

                #region 填充内容

                int j = ;
                IRow dataRow = sheet1.CreateRow(rowIndex);
                foreach (DataColumn column in table_data.Columns)
                {
                    ICell newCell = dataRow.CreateCell(column.Ordinal);

                    string drValue = row[column].ToString();

                    switch (column.DataType.ToString())
                    {
                        case "System.String"://字符串类型
                            newCell.SetCellValue(drValue);
                            newCell.CellStyle = stringStyle;
                            break;
                        case "System.Double":
                            if (drValue != "")
                            {
                                double doubV = ;
                                double.TryParse(drValue, out doubV);
                                newCell.SetCellValue(doubV);
                            }
                            else
                            {
                                newCell.SetCellValue("");
                            }
                            newCell.CellStyle = cellStyle;
                            break;
                    }

                    #region 单元格合并（这里只合并第一列）

                        if (j ==  && temp_col1 != drValue)
                        {
                            if (temp_col1 != "")
                            {
                                sheet1.AddMergedRegion(new CellRangeAddress(col1_s, rowIndex - , , ));
                            }
                            temp_c1 = drValue;
                            col1_s = rowIndex;
                        }

                    #endregion

                    j++;
                }
                #endregion

                rowIndex++;
            }

            //冻结窗口  锁定表头和第一列
            sheet1.CreateFreezePane(, , , );

            //输出
            context.Response.ContentType = "application/vnd.ms-excel";
            context.Response.AddHeader("Content-Disposition", string.Format("attachment;filename={0}", "mayixue的NPOI测试.xls"));
            context.Response.Clear();

            MemoryStream file = new MemoryStream();
            hssfworkbook.Write(file);
            file.WriteTo(context.Response.OutputStream);
            context.Response.End();
        }

再来看下导入Excel到DataTable

/// <summary>
        /// 读取Excel文件到DataSet中
        /// </summary>
        /// <param name="filePath">文件路径</param>
        /// <returns></returns>
        private DataTable ExcelToDataTable(string filePath)
        {
            DataTable dt = new DataTable();

            HSSFWorkbook hssfworkbook;
            using (FileStream file = new FileStream(filePath, FileMode.Open, FileAccess.Read))
            {
                hssfworkbook = new HSSFWorkbook(file);
            }
            ISheet sheet = hssfworkbook.GetSheetAt();
            System.Collections.IEnumerator rows = sheet.GetRowEnumerator();

            IRow headerRow = sheet.GetRow();
            int cellCount = headerRow.LastCellNum;

            for (int j = ; j < cellCount; j++)
            {
                ICell cell = headerRow.GetCell(j);
                dt.Columns.Add(cell.ToString());
            }

            for (int i = (sheet.FirstRowNum + ); i <= sheet.LastRowNum; i++)
            {
                IRow row = sheet.GetRow(i);
                DataRow dataRow = dt.NewRow();

                for (int j = row.FirstCellNum; j < cellCount; j++)
                {
                    if (row.GetCell(j) != null)
                        dataRow[j] = row.GetCell(j).ToString();
                }

                dt.Rows.Add(dataRow);
            }
            return dt;
        }

NPOI升级后语法上有些变动（这个例子中红色标注地方），（我是从1.2.2直接更新到2.0的，期间发生过什么这里不做描述）

这个例子的实现，离不开优秀文章的帮助，在这里向作者表示感谢。

参考文章：

.net 使用NPOI或MyXls把DataTable导出到Excel

NPOI - Initialisation of record 0x862 left 2 bytes remaining still to be read.

POI设置EXCEL单元格格式为文本、小数、百分比、货币、日期、科学计数法和中文大写

用NPOI操作EXCEL－－锁定列