public class ExportHelper

    {

        public static Stream RenderDataTableToExcel(DataTable SourceTable)

        {

            HSSFWorkbook workbook = new HSSFWorkbook();

            MemoryStream ms = new MemoryStream();

            HSSFSheet sheet = workbook.CreateSheet();

            HSSFRow headerRow = sheet.CreateRow();

            // handling header.

            foreach (DataColumn column in SourceTable.Columns)

                headerRow.CreateCell(column.Ordinal).SetCellValue(column.ColumnName);

            // handling value.

            int rowIndex = ;

            foreach (DataRow row in SourceTable.Rows)

            {

                HSSFRow dataRow = sheet.CreateRow(rowIndex);

                foreach (DataColumn column in SourceTable.Columns)

                {

                    dataRow.CreateCell(column.Ordinal).SetCellValue(row[column].ToString());

                }

                rowIndex++;

            }

            workbook.Write(ms);

            ms.Flush();

            ms.Position = ;

            sheet = null;

            headerRow = null;

            workbook = null;

            return ms;

        }

        public static DataTable RenderDataTableFromExcel(Stream ExcelFileStream, int SheetIndex, int HeaderRowIndex)

        {

            HSSFWorkbook workbook = new HSSFWorkbook(ExcelFileStream);

            HSSFSheet sheet = workbook.GetSheetAt(SheetIndex);

            DataTable table = new DataTable();

            HSSFRow headerRow = sheet.GetRow(HeaderRowIndex);

            int cellCount = headerRow.LastCellNum;

            for (int i = headerRow.FirstCellNum; i < cellCount; i++)

            {

                DataColumn column = new DataColumn(headerRow.GetCell(i).StringCellValue);

                table.Columns.Add(column);

            }

            int rowCount = sheet.LastRowNum;

            for (int i = (sheet.FirstRowNum + ); i <= sheet.LastRowNum; i++)

            {

                HSSFRow row = sheet.GetRow(i);

                DataRow dataRow = table.NewRow();

                for (int j = row.FirstCellNum; j < cellCount; j++)

                {

                    if (row.GetCell(j) != null)

                        dataRow[j] = row.GetCell(j).ToString();

                }

                table.Rows.Add(dataRow);

            }

            ExcelFileStream.Close();

            workbook = null;

            sheet = null;

            return table;

        }

    }

protected void exportExcelFun(){

        DataTable dt=new DataTable();

        dt=XXXXX;//Use ADO.NET to get Data from DB

        MemoryStream ms = ExportHelper.RenderDataTableToExcel(dt) as MemoryStream;

        /*情况1：在Asp.NET中，输出文件流，浏览器自动提示下载*/

        Response.AddHeader("Content-Disposition", string.Format("attachment; filename=download.xls"));

        Response.BinaryWrite(ms.ToArray());

        ms.Close();

        ms.Dispose();

        /*情况2：在Winform中，弹出SaveFileDialog，提示用户选择文件放置位置。*/

         string saveFileName = "";

         bool fileSaved = false;

         SaveFileDialog saveDialog = new SaveFileDialog();

         saveDialog.DefaultExt = "xls";

         saveDialog.Filter = "Excel文件|*.xls";

         saveDialog.FileName = "download";

         saveDialog.ShowDialog();

         saveFileName = saveDialog.FileName;

         if (saveFileName.IndexOf(":") < 0) return; //被点了取消

         if (saveFileName != ""){

               try{

                    FileStream fs = new FileStream(saveDialog.FileName, FileMode.Create);

                    fs.Write(ms.GetBuffer(), 0, ms.GetBuffer().Length);

                    ms.Close();

                    ms.Dispose();

                    fs.Close();

                    fileSaved = true;

                }

                catch (Exception ex){

                    fileSaved = false;

                    MessageBox.Show("导出文件时出错,文件可能正被打开！\n" + ex.Message);

                }

          }

          else{

                fileSaved = false;

          }

          GC.Collect();//强行销毁

          if (fileSaved && File.Exists(saveFileName)){

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

          }

          else {

                 MessageBox.Show("导出失败！", "通知");

          }

}               

protected void importExcelFun(){

    /*情况1：在Asp.net网站，一般使用asp:FileUpLoad控件(实际上是一个HTML表单.input:type=file)上传文件*/

    if(this.FileUpLoader.HasFile){

        DataTable dt=new DataTable();
　　　　　//设置第1行为标题行，从第二行开始读取数据。标题行作为DataTable表头。

        dt=ExcelHelper.RenderDataTableFromExcel(this.FileUpLoader.FileContent,,);
　　　　　//use dt to do something

    }

    /*情况2：在Winform中，*/

     OpenFileDialog fileDialog = new OpenFileDialog();

     fileDialog.Filter = "Excel文件|*.xls";

     fileDialog.InitialDirectory = "E:\\";//设置默认打开路径

     if (fileDialog.ShowDialog() == DialogResult.OK){

         string fileName=fileDialog.FileName;//得到文件所在位置。
　　　　　// use c# to read Excel File as Steam.
　　　　　// use ExcelHelper for converting Stream to DataTable.

     }

}