从sql中读取文件下载选择保存地址的问题

Question

SqlConnection objCn = new SqlConnection("server=.;database=;uid=;pwd=");        objCn.Open();        SqlCommand cm = new SqlCommand("select contents from fileup where ID=3",objCn);        SqlDataReader dr = cm.ExecuteReader();        byte[] File = null;        if (dr.Read())        {            File = (byte[])dr[0];        }        FileStream fs;        FileInfo fi = new System.IO.FileInfo("文件");        fs = fi.OpenWrite();        fs.Write(File, 0, File.Length);        fs.Close();     这是我从数据库读取文件保存到本地的代码  它默认保存到网站的跟目录下  要如何能够让用户点击下载时 选择保存的路径呢！！！