产生随机不重复ID

 /// <summary>
/// Decimal 27位ID生成规则（前面17位为时间，后面10位为随机生成数）：
/// </summary>
/// <returns></returns>
        public decimal GeneratePk()
        {
            Guid id = Guid.NewGuid();
byte[] byid = id.ToByteArray();

uint uid = BitConverter.ToUInt32(byid, 12);
string strid = DateTime.Now.ToString("yyyyMMddHHmmssfff") + uid.ToString("D10");

return decimal.Parse(strid);
        }