前文写了一个BS版本号的导出Excel的样例（http://blog.csdn.net/yysyangyangyangshan/article/details/47904119）。对于CS版在保存的地方有少许修改。直接看代码例如以下：
   

      private void button1_Click(object sender, EventArgs e)

        {

            //要保存的内容。此处用代码生成的内容，而在实际中能够是数据库读取的，

            //亦或是页面输入的内容

            DataTable dt = new DataTable();

            dt.Columns.Add("序号");

            dt.Columns.Add("姓名");

            dt.Columns.Add("年龄");

            dt.Columns.Add("职位");

            for (int i = 0; i < 5; i++)

            {

                DataRow row = dt.NewRow();

                row["序号"] = i + 1;

                row["姓名"] = "Test" + i;

                row["年龄"] = 25 + i;

                row["职位"] = i % 2 == 0 ? "project师" : "经理";

                dt.Rows.Add(row);

            }

            //为了更好的看怎样使用NPOI。此处显示两行标题。

            //显示标题能够看怎样合并单元格

            string mainTitle = "主标题";

            string secondTitle = "副标题";

            //保存的Excel路径，文件名称用guid生成

            string fileIndex = System.AppDomain.CurrentDomain.BaseDirectory;

            string tempExcel = fileIndex + @"\ExcelFile\{0}.xls";

            tempExcel = string.Format(tempExcel, System.Guid.NewGuid());

            int rowIndex = 0;

            //操作Excel的几个主要对象。此处声明

            HSSFWorkbook workbook = new HSSFWorkbook();

            HSSFSheet sheet = workbook.CreateSheet();

            //row0和row1是两行标题

            HSSFRow row0 = sheet.CreateRow(rowIndex);

            HSSFCell cell0 = row0.CreateCell(0);

            cell0.SetCellValue(mainTitle);

            HSSFCellStyle style = workbook.CreateCellStyle();

            style.Alignment = CellHorizontalAlignment.CENTER;

            HSSFFont font = workbook.CreateFont();

            font.Boldweight = short.MaxValue;

            style.SetFont(font);

            cell0.CellStyle = style;

            //此处合并单元格

            sheet.AddMergedRegion(new NPOI.HSSF.Util.CellRangeAddress(rowIndex, rowIndex, 0, 5));

            rowIndex++;

            HSSFRow row1 = sheet.CreateRow(rowIndex);

            HSSFCell cell1 = row1.CreateCell(0);

            cell1.SetCellValue(secondTitle);

            cell1.CellStyle = style;

            sheet.AddMergedRegion(new NPOI.HSSF.Util.CellRangeAddress(rowIndex, rowIndex, 0, 5));

            //由于列名已经指定。占一行

            rowIndex++;

            //这一行显示表头

            HSSFRow row2 = sheet.CreateRow(rowIndex);

            int row2cellIndex = 0;

            foreach (DataColumn col in dt.Columns)

            {

                HSSFCell cell = row2.CreateCell(row2cellIndex);

                cell.SetCellValue(col.ColumnName.ToString());

                row2cellIndex++;

            }

            rowIndex++;

            //datatable的内容

            for (int i = 0; i < dt.Rows.Count; i++)

            {

                HSSFRow row = sheet.CreateRow(rowIndex);

                foreach (DataColumn col in dt.Columns)

                {

                    row.CreateCell(col.Ordinal).SetCellValue(dt.Rows[i][col].ToString());

                }

                rowIndex++;

            }

            //使用文件流保存

            MemoryStream ms = new MemoryStream();

            workbook.Write(ms);

            ms.Flush();

            ms.Position = 0;

            workbook = null;

            sheet = null;

            FolderBrowserDialog dialog = new FolderBrowserDialog();

            dialog.Description = "请选择文件路径";

            if (dialog.ShowDialog() == DialogResult.OK)

            {

                string saveFile = dialog.SelectedPath+@"\TestExcel.xls";

                using (FileStream fs = new FileStream(tempExcel, FileMode.Create, FileAccess.ReadWrite))

                 {

                     ms.WriteTo(fs);

                 }

                File.Copy(tempExcel, saveFile, true);

                MessageBox.Show("导出成功。");

            }

            if (File.Exists(tempExcel))

            {

                File.Delete(tempExcel);

            }

            ms.Close();

        }

使用保存对话框进行保存：

         FolderBrowserDialog dialog = new FolderBrowserDialog();

            dialog.Description = "请选择文件路径";

            if (dialog.ShowDialog() == DialogResult.OK)

            {

                string saveFile = dialog.SelectedPath+@"\TestExcel.xls";

                using (FileStream fs = new FileStream(tempExcel, FileMode.Create, FileAccess.ReadWrite))

                 {

                     ms.WriteTo(fs);

                 }

                File.Copy(tempExcel, saveFile, true);

                MessageBox.Show("导出成功！");

            }

这样在窗体中也能够实现导出Excel。
project下载：http://download.csdn.net/detail/yysyangyangyangshan/9039017