C#隐藏文件下载路径的方法

 关于下载路径的隐藏都是通过传递一个数据库中的ID，然后在另外一张页面通过传递的ID在数据库中读出路径。
c#中实现的方法（只需要.ASPX.CS的代码就可以了）

string sel_sql="select FileVisualPath from TabMailAttachFiles where FileID="+Request.QueryString["destFileName"].ToString();

//   string destFileName = Request.QueryString["destFileName"]!=null?Request.QueryString["destFileName"]:"";
   string destFileName=ROA.Components.fune_commerce.Execad(sel_sql).Tables[0].Rows[0][0].ToString();
   destFileName = Server.MapPath(".")+destFileName;
   destFileName = Server.UrlDecode(destFileName);
   if(File.Exists(destFileName))
   {
    FileInfo fi = new FileInfo(destFileName);
    Response.Clear();
    Response.ClearHeaders();
    Response.Buffer = false;
    
    //Response.AppendHeader("Content-Disposition","attachment;filename=" +HttpUtility.UrlEncode(Path.GetFileName(destFileName),System.Text.Encoding.Default));
    Response.AppendHeader("Content-Disposition","attachment;filename=" +HttpUtility.UrlEncode(Path.GetFileName(destFileName),System.Text.Encoding.UTF8));
    Response.AppendHeader("Content-Length",fi.Length.ToString());
    Response.ContentType="application/octet-stream";
    Response.WriteFile(destFileName);
    Response.Flush();
    Response.End();
   }
   else
   {
    Response.Write("<script langauge=javascript>alert('文件不存在!');history.go(-1);</script>");
    Response.End();
   }