（急）c#生成execl 后，无法读取档案

Question

我采用不通过OLE生成excel文件的方法生成execl,可是解压后重新计算格式时，出错“无法打开档案”
有的单元格字符很长，所以，请高手帮忙修改
    string timeFlag = DateTime.Now.ToFileTime().ToString();
            string dirStr = path + DateTime.Now.ToFileTime().ToString();
            System.IO.Directory.CreateDirectory(dirStr);
            int fileNum = 1;
            //不通过OLE生成excel文件的方法          
            for (int index = 0; index < list.Count; index++)
            {
                ProblemCodeExcel excel = new ProblemCodeExcel(GenFileName(dirStr + "\\"));
                excel.BeginWrite();
                excel.WriteHeader();
               
                Console.WriteLine("正在生成第" + fileNum.ToString() + "个文档.....");
                for (ushort row = 1; row < ushort.MaxValue && index < list.Count; row++, index++)
                {
              if (list[index] != null)
                    {
                        excel.WriteString(row, 0, list[index].CreateDate);
                        excel.WriteString(row, 1, list[index].CaseId);
                        excel.WriteString(row, 2, list[index].Country);
                        excel.WriteString(row, 3, list[index].Datasource);
                        excel.WriteString(row, 4, list[index].Engineer);
                        excel.WriteString(row, 5, list[index].Model);
                        excel.WriteString(row, 6, list[index].Problem);
                        excel.WriteString(row, 7, list[index].ProblemCode);
                        excel.WriteString(row, 8, list[index].ProblemDesc);
                        excel.WriteString(row, 9, list[index].ProblemType);
                        excel.WriteString(row, 10, list[index].ProblemTypeDesc);
                        excel.WriteString(row, 11, list[index].ProductType);
                        excel.WriteString(row, 12, list[index].Reply);
                        excel.WriteString(row, 13, list[index].Series);
                        excel.WriteString(row, 14, list[index].Server);
                        excel.WriteString(row, 15, list[index].Subject);
                        excel.WriteString(row, 16, list[index].SubSeries);
                    }
                    else
                        break;                }
                Console.WriteLine("生成成功！");
             
                index--;
                fileNum++;  
                excel.EndWrite();
            }            ZipDAO dao = new ZipDAO(dirStr);
            dao.ZipFold();
            DeleteFile(dirStr);
            Console.WriteLine("处理完毕");
            Thread.Sleep(1000);
            return virtualPath + timeFlag + ".rar";
        }        private static string GenFileName(string phycialPath)
        {
            string timeFlag = DateTime.Now.ToFileTime().ToString();
            return phycialPath + timeFlag + ".xls";
        } public class ExcelWriter
    {
        System.IO.FileStream _wirter;
        public ExcelWriter(string strPath)
        {
            _wirter = new System.IO.FileStream(strPath, System.IO.FileMode.OpenOrCreate);
        }
        /// <summary>
        /// 写入short数组
        /// </summary>
        /// <param name="values"></param>
        private void _writeFile(ushort[] values)
        {
            foreach (ushort v in values)
            {
                byte[] b = System.BitConverter.GetBytes(v);
                _wirter.Write(b, 0, b.Length);
            }
        }
        /// <summary>
        /// 写文件头
        /// </summary>
        public void BeginWrite()
        {
            _writeFile(new ushort[] { 0x809, 8, 0, 0x10, 0, 0 });
        }
        /// <summary>
        /// 写文件尾
        /// </summary>
        public void EndWrite()
        {
            _writeFile(new ushort[] { 0xa, 0 });
            _wirter.Close();
        }
        /// <summary>
        /// 写一个数字到单元格x,y
        /// </summary>
        /// <param name="x"></param>
        /// <param name="y"></param>
        /// <param name="value"></param>
        public void WriteNumber(ushort x, ushort y, double value)
        {
            _writeFile(new ushort[] { 0x203, 14, x, y, 0 });
            byte[] b = System.BitConverter.GetBytes(value);
            _wirter.Write(b, 0, b.Length);
        }
        /// <summary>
        /// 写一个字符到单元格x,y
        /// </summary>
        /// <param name="x"></param>
        /// <param name="y"></param>
        /// <param name="value"></param>
        public void WriteString(ushort x, ushort y, string value)
        {
            byte[] b = System.Text.Encoding.Default.GetBytes(value);
            _writeFile(new ushort[] { 0x204, (ushort)(b.Length + 8), x, y, 0, (ushort)b.Length });
            _wirter.Write(b, 0, b.Length);
            
        }
    }