ASP.NET cookie不写？重定向问题？

Question

我有以下代码：

                var serializer = new XmlSerializer(typeof(classes.Member));
                TextWriter writer = new StringWriter();
                serializer.Serialize(writer, active_resident);

                HttpCookie cookie = Request.Cookies["ActiveUser"];
                if (cookie == null)
                {
                    cookie = new HttpCookie("ActiveUser");
                }

                cookie.Expires = DateTime.Now.AddHours(1);
                cookie.Value = Genesis.Encryption.EncryptAES(writer.ToString(), Genesis.Generic.ReadAppSettingsValue("GenesisEncryptionKey"));
                Response.Cookies.Add(cookie);
                writer.Close();

                // Redirect to Secure Area
                Response.Redirect("secure/dashboard.aspx", false);

奇怪的是，cookie不是写的？但是，ASP.Net Session cookie是？有什么想法吗？