protected void Page_Load(object sender, EventArgs e)
        {
                if (!IsPostBack)
                {
                    if (Request.UrlReferrer != null)
                            ViewState["ReferrerUrl"] = Request.UrlReferrer.ToString();
                }
        }

        protected void btnUpdate_Click(object sender, EventArgs e)
        {
        //...你的更新操作

                if (ViewState["ReferrerUrl"] != null)
                    Response.Redirect(ViewState["ReferrerUrl"].ToString());
                else
                    Response.Redirect("default.aspx");

        }