asp.net alert之后才跳转页面

/// <summary>
        /// 弹出对话框 并且跳转界面
        /// </summary>
        /// <param name="page">Page或者this</param>
        /// <param name="str">值 如'登陆成功!'</param>
        /// <param name="url">要跳转的界面 如'admin/main.aspx'</param>
        public static void show(Page page, string str, string url)
        {
            page.ClientScript.RegisterStartupScript(page.GetType(), "", "<script language=javascript>alert('" + str + "');location.href='" + url + "';</script>");
        }