将所选数据保存到Cookie中失败

Question

我有一些下拉菜单供您选择日期。问题是选择日期后，用户需要登录。此后，刷新选择日期的所有成员日期会话都丢失了（不仅是js，而且由于相关的选择，很多日期到来了。

我试图将选定的项目保存在cookie中，但是没有用。

我有索引的会话

private int getIndexFromSession()
{
    int index = 0;
    if (Session["DTF_selectedIndex"] != null)
    {
        index = (int)Session["DTF_selectedIndex"];
        // Session.Remove("DTF_selectedIndex");
        if (index > dateTimeFilter.Items.Count)
            index = 0;
    }
    return index;
}

.aspx中的下拉列表：

<asp:DropDownList ID="dateTimeFilter" runat="server"  OnSelectedIndexChanged="dateTimeFilter_SelectedIndexChanged"

和.cs

protected void dateTimeFilter_SelectedIndexChanged(object sender, EventArgs e)
{
    //   showsDatalistPanel.Visible = true;
    DropDownList ddl = (DropDownList)sender;

    if (ddl.SelectedValue != "0")
    {
        Session["DTF_selectedIndex"] = ddl.SelectedValue;
        HttpCookie cookie = new HttpCookie("DTF_selectedIndex", ddl.SelectedValue);
        DateTime now = DateTime.Now;

        cookie.Expires = now.AddMinutes(10);

        Response.Cookies.Add(cookie);
    }
}

和请求

protected void Page_Load(object sender, EventArgs e)
{  
    if (Session["DTF_selectedIndex"] != null)
    {
        Session["DTF_selectedIndex"] = Request.Cookies["DTF_selectedIndex"];       
    }
}