SqlConnection con=new SqlConnection("server=.;database=study;uid=sa;pwd=sa");
            con.Open();
            string sql="select * from download where fileID='"+fileID+"'";
            SqlCommand cmd=new SqlCommand(sql,con);
            SqlDataReader sdr=cmd.ExecuteReader();
                sdr.Read();
                Response.Buffer=true;
                Page.Response.Clear();//清除缓冲区所有内容
                Page.Response.ContentType="application/octet-stream";                Page.Response.AddHeader("Content-Disposition","attachment;filename="+HttpUtility.UrlEncode(sdr["fileName"].ToString()));
                byte[] file=(Byte[])sdr["fileData"];//读出数据
                int a=file.Length;
                Response.BinaryWrite(file);
                Response.Flush();
                Response.End();        
            sdr.Close();
            con.Close();