how to download file from gridview

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "download")
        {
            Session["sid"] = e.CommandArgument.ToString();
            if (sconn.State == ConnectionState.Open)
            {
                sconn.Close();
            }
            sconn.Open();
            string qry = "Select  FIle from File_Table where Id='" + Session["sid"].ToString() + "' ";
            SqlCommand cmd = new SqlCommand(qry, sconn);
            SqlDataReader dr = cmd.ExecuteReader();
            DataTable dt = new DataTable();
            dt.Load(dr);

            string fName = dt.Rows[0][0].ToString();

            cmd.ExecuteNonQuery();
            sconn.Close();
            if (fName == "")
            {
                ScriptManager.RegisterStartupScript(this, this.GetType(), "message", "alert('No Download Link Found');", true);
            }
            else
            {
                Response.Write("<script>alert('" + fName + "')</script>");
                Response.ContentType = "application/octet-stream";
                Response.AddHeader("Content-Disposition", "attachment;filename=" + fName);
                Response.TransmitFile(Server.MapPath("~/Files/" + fName));
                Response.End();
            }
        }
    }

// This button click event is used to download files from gridview

       protected void lnkDownload_Click(object sender, EventArgs e)
       {
           LinkButton lnkbtn = sender as LinkButton;
           GridViewRow gvrow = lnkbtn.NamingContainer as GridViewRow;
           string filePath = gvDetails.DataKeys[gvrow.RowIndex].Value.ToString();
           Response.ContentType = "image/jpg";
           Response.AddHeader("Content-Disposition", "attachment;filename=\"" + filePath + "\"");
           Response.TransmitFile(Server.MapPath(filePath));
           Response.End();