【关于登陆cookies】的有关问题

【关于登陆cookies】的问题
当我关闭浏览器 从新打开浏览器的时候 就找不到cookie 说明我保存失败了.请问我该哪里写错了该怎么修改

C# code

            if (this.ddlstatus.SelectedValue == "普通用户")            {                if (BaseClass.CheckStudent(txtNum.Text.Trim(), txtPwd.Text.Trim()))                {                    Session["ID"] = txtNum.Text.Trim();                    Session["name"] = txtNum.Text.Trim();                    HttpCookie littcookie = new HttpCookie("UserloginName");                    Response.Cookies["UserloginName"].Value = HttpUtility.UrlEncode(txtNum.Text, System.Text.Encoding.GetEncoding("gb2312"));                     //Cookies保存用户名                    Response.Cookies["UserloginName"].Expires = DateTime.Today.AddDays(30);  //设置过期时间，                     Tb_Student tb_Student = Tb_StudentManager.Instance.GetModelTb_StudentByWhere(" StudentNum='" + txtNum.Text.ToString() + "' ");                    Session["danwei"] =tb_Student.Danwei.ToString();                    Session["keshi"] = tb_Student.Keshi.ToString();//科室                    Session["shouji"] = tb_Student.Tel.ToString();//科室                    Response.Redirect("student/studentexam.aspx");                }

C# code

  try            {                if (Request.Cookies["UserloginName"] != null)                {                   string nemaeusel = HttpUtility.UrlDecode(Request.Cookies["UserloginName"].Value, System.Text.Encoding.GetEncoding("gb2312"));                }

C# code

HttpCookie cookie = new HttpCookie("test");      cookie.Value = "二哥";      cookie.Expires = DateTime.Now.AddDays(1);      Response.Cookies.Add(cookie);