HSSFWorkbook hssfworkbook;        void InitializeWorkbook(string path)        {            //read the template via FileStream, it is suggested to use FileAccess.Read to prevent file lock.            //book1.xls is an Excel-2007-generated file, so some new unknown BIFF records are added.             using (FileStream file = new FileStream(path, FileMode.Open, FileAccess.Read))            {                hssfworkbook = new HSSFWorkbook(file);            }        }        DataSet ConvertToDataTable()        {            // ISheet sheet = hssfworkbook.GetSheetAt(0);            DataSet dataSet1 = new DataSet();            foreach (ISheet sheet in hssfworkbook)            {                DataTable dt = new DataTable();                int columnCount = 0;                foreach (HSSFRow row in sheet)                {                    columnCount = Math.Max(columnCount, row.LastCellNum);                }                for (int j = 0; j < columnCount; j++)                {                    dt.Columns.Add(Convert.ToChar(((int)'A') + j).ToString());                }                foreach (HSSFRow row in sheet)                {                    DataRow dr = dt.NewRow();                    for (int i = 0; i < columnCount; i++)                    {                        ICell cell = row.GetCell(i);                        dr[i] = cell == null ? "" : cell.ToString();                    }                    dt.Rows.Add(dr);                }                dataSet1.Tables.Add(dt);            }            return dataSet1;        }        private void btnImport_Click(object sender, EventArgs e)        {            InitializeWorkbook(@"xls\A499ANN636412MO.xls");            DataSet dataSet1 = ConvertToDataTable();            dataGridView1.DataSource = dataSet1.Tables[0];        }

读取一个Excel 的多个 Sheet  并放到一个 DataSet 里。

当写 byte[] 时，要使用 ms.ToArray(); 而不要使用 ms.GetBuffer();

前者虽然稍慢，但不会在 Excel 文件中形成很多空字节。