protected void Linkbtn_Click(object senter, EventArgs e)
    {
        int jID = Convert.ToInt32(((LinkButton)senter).CommandArgument);
        string loginName = Session["TacherName"].ToString();
        string TrueName = bll_tem.GetTeachersDatabaseById(jID).JTrueName;
        string path = "~/UsersFolder/Teacher/" + loginName + "/" + TrueName;

        Response.ContentType = "application/x-zip-compressed";
        Response.AddHeader("Content-Disposition", "attachment;filename="+TrueName);
        string file = Server.MapPath(path);
        Response.TransmitFile(file);
    }