生成唯一ID 由数字组成

/// <summary>
        /// 生成唯一ID
        /// </summary>
        /// <returns></returns>
        public static string CreateIDCode()
        {
            DateTime Time1 = DateTime.Now.ToUniversalTime();
            DateTime Time2 = Convert.ToDateTime("1970-01-01");
            TimeSpan span = Time1 - Time2;   //span就是两个日期之间的差额   
            string t = span.TotalMilliseconds.ToString("0");

            return t;
        }