c# 返回页面

protected void Page_Load(object sender, EventArgs e)
    {
        Page.Title = DataClass.GetApplication("webname") + " - " + "系统信息";
        string strID=Request.QueryString["id"];
        if(!IsPostBack)
        {
            switch (strID)
            {
                case "1":
                    Lbl_prompt.Text += "注册成功";
                    Hlk_Link.Text = "返回首页";
                    Hlk_Link.NavigateUrl = "index.aspx";
                    break;

                case "2":
                    Lbl_prompt.Text += "用户名已存在，请重新设置";
                    break;

                case "3":
                    Lbl_prompt.Text += "Email已存在，请重新设置";
                    break;

                case "4":
                    Lbl_prompt.Text += "用户名或密码有误，请重新登录";
                    Hlk_Link.Text = "返回登录页";
                    Hlk_Link.NavigateUrl = "login.aspx";
                    Response.Write("<script language='javascript'>setTimeout(\"{location.href='login.aspx'}\",5000);</script>");
                    break;

                case "5":
                    Lbl_prompt.Text += "登录成功";
                    Hlk_Link.Text = "返回首页";
                    Hlk_Link.NavigateUrl = "index.aspx";
                    Response.Write("<script language='javascript'>setTimeout(\"{location.href='index.aspx'}\",5000);</script>");
                    break;

                case "6":
                    Lbl_prompt.Text += "您已经安全退出";
                    Hlk_Link.Text = "返回首页";
                    Hlk_Link.NavigateUrl = "index.aspx";
                    Response.Write("<script language='javascript'>setTimeout(\"{location.href='index.aspx'}\",5000);</script>");
                    break;

                case "7":
                    Lbl_prompt.Text += "您已经成功发布信息";
                    Hlk_Link.Text = "返回首页";
                    Hlk_Link.NavigateUrl = "index.aspx";
                    Response.Write("<script language='javascript'>setTimeout(\"{location.href='index.aspx'}\",5000);</script>");
                    break;
                case "8":
                    Lbl_prompt.Text += "修改成功";
                    break;

                case "9":
                    Lbl_prompt.Text += "您尚未登录，请登录后使用";
                    Hlk_Link.Text = "返回登录页";
                    Hlk_Link.NavigateUrl = "login.aspx";
                    Response.Write("<script language='javascript'>setTimeout(\"{location.href='login.aspx'}\",5000);</script>");
                    break;

                case "10":
                    Lbl_prompt.Text += "修改成功";
                    Hlk_Link.Text = "返回用户中心";
                    Hlk_Link.NavigateUrl = "usercenter.aspx";
                    Response.Write("<script language='javascript'>setTimeout(\"{location.href='usercenter.aspx'}\",5000);</script>");
                    break;
                case "11":
                    Lbl_prompt.Text += "用户名或密码有误，请重新登录";
                    Hlk_Link.Text = "返回登录页";
                    Hlk_Link.NavigateUrl = "login.aspx";
                    Response.Write("<script language='javascript'>setTimeout(\"{location.href='login.aspx'}\",5000);</script>");
                    break;

                default:
                    break;