asp.net文件下载

       protected void btn_Down(object sender, EventArgs e)
         {
             string filePath = Server.MapPath("/TradeLog/" + txtDate.Text.Trim());
             if (!downBeforeValidation(filePath))
                 return;
             dlZipDir(filePath, txtDate.Text);
         }    

        /// <summary>
         /// 下载前验证
         /// </summary>
         /// <param name="filePath">文件路径</param>
         /// <returns></returns>
         private bool downBeforeValidation(string filePath)
         {
             //判断密码是否正确
             string downPassWord = WebConfigurationManager.AppSettings["downPassWord"];
             if (string.IsNullOrEmpty(txtPassWord.Text) || txtPassWord.Text.Trim() != downPassWord)
             {
                 Response.Write("<script>alert('密码错误或为空')</script>");
                 return false;
             }
             //判断文件是否存在

             if (!Directory.Exists(filePath))
             {
                 Response.Write("<script>alert('目录不存在')</script>");
                 return false;
             }
             return true;
         }

       /// <summary>
         /// 全部变量
         /// </summary>
         ZipOutputStream zos = null;
         String strBaseDir = "";
         /// <summary>
         /// 下载文件
         /// </summary>
         /// <param name="strPath">路径</param>
         /// <param name="strFileName">下载后默认显示文件名称</param>
         void dlZipDir(string strPath, string strFileName)
         {
             MemoryStream ms = null;
             Response.ContentType = "application/octet-stream";
             strFileName = HttpUtility.UrlEncode(strFileName).Replace('+', ' ');
             Response.AddHeader("Content-Disposition", "attachment;   filename=" + strFileName + ".zip");
             ms = new MemoryStream();
             zos = new ZipOutputStream(ms);
             strBaseDir = strPath + "\\";
             addZipEntry(strBaseDir);
             zos.Finish();
             zos.Close();
             Response.Clear();
             Response.BinaryWrite(ms.ToArray());
             Response.End();
         }

      /// <summary>
         /// 生成压缩文件
         /// </summary>
         /// <param name="PathStr"></param>
         void addZipEntry(string PathStr)
         {
             DirectoryInfo di = new DirectoryInfo(PathStr);
             foreach (DirectoryInfo item in di.GetDirectories())
             {
                 addZipEntry(item.FullName);
             }
             foreach (FileInfo item in di.GetFiles())
             {
                 FileStream fs = File.OpenRead(item.FullName);
                 byte[] buffer = new byte[fs.Length];
                 fs.Read(buffer, , buffer.Length);
                 string strEntryName = item.FullName.Replace(strBaseDir, "");
                 ZipEntry entry = new ZipEntry(strEntryName);
                 zos.PutNextEntry(entry);
                 zos.Write(buffer, , buffer.Length);
                 fs.Close();
             }
         }