I have assigned some values to session and wants to access in jquery method , but i am getting null in session.

public ActionResult SaveData(string Idpro,string IdDescription)
{
    //some operation here 
    Session["UserNameDateTime"] = Product.Updated + " " + Product.DateModified;
    return null;
}

$.ajax({
    url: '@Url.Action("SaveData")' + '?Idpro=' + ProductId + '&IdDescription=' + Description + '&def=' + def,
    success: function (result) {
        $('#modal-container').modal("hide");
        var userNamePassword = '@Session["UserNameDateTime"]';
    }
});

Please help ....