C#从数据库下载二进制存储图片的方法

二进制图片
            DataTable dt = new DataTable();
            string sql = "select binary from biao";
            SqlConnection cn = new SqlConnection();
            SqlDataAdapter dat = new SqlDataAdapter(sql, cn);
            dat.Fill(dt);
            byte[] by=(byte[])dt.Rows[0][0];
            Response.AddHeader("Content-Disposition", "attachment;  filename=aaa.jpg");
            Response.AddHeader("Content-length", by.Length.ToString());
            Response.ContentType = "image/jpg";
            Response.OutputStream.Write(by, 0, by.Length);
            Response.Flush();
            Response.End();

地址图片
 protected void A(object sender, EventArgs e)
        {
            string cc = Request["StudentId"];
            MISDataContext dt = new MISDataContext();（linq to sql）
            Students s = dt.Students.Where(c => c.StudentId == cc).FirstOrDefault();
            string path = " ";
            path = s.Photo;
            //string filename = s.StudentName;
            if (path ==null)
            {
                Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", "<script>alert('没有证件照片，请上传过再下载')</script>");
            }
            else
            {
                DownLoad(path);