C#如何生成唯一订单号

/// <summary>
  /// 生成唯一数
  /// </summary>
  public class UniqueData
  {
    private static object obj = new object();
    private static int GuidInt { get { return Guid.NewGuid().GetHashCode(); } }
    private static string GuidIntStr { get { return Math.Abs(GuidInt).ToString(); } }

    /// <summary>
    /// 生成
    /// </summary>
    /// <param name="mark">前缀</param>
    /// <param name="timeType">时间精确类型 1 日,2 时,3 分，4 秒(默认) </param>
    /// <param name="id">id 小于或等于0则随机生成id</param>
    /// <returns></returns>
    public static string Gener(string mark, int timeType = 4, int id = 0)
    {
      lock (obj)
      {
        var number = mark;
        var ticks = (DateTime.Now.Ticks - GuidInt).ToString();
        int fillCount = 0;//填充位数

        number += GetTimeStr(timeType, out fillCount);
        if (id > 0)
        {
          number += ticks.Substring(ticks.Length - (fillCount + 3)) + id.ToString().PadLeft(10, '0');
        }
        else
        {
          number += ticks.Substring(ticks.Length - (fillCount + 3)) + GuidIntStr.PadLeft(10, '0');
        }
        return number;
      }
    }

    /// <summary>
    /// 生成
    /// </summary>
    /// <param name="mark">前缀</param>
    /// <param name="timeType">时间精确类型 1 日,2 时,3 分，4 秒(默认)</param>
    /// <param name="id">id 小于或等于0则随机生成id</param>
    /// <returns></returns>
    public static string GenerLong(string mark, int timeType = 4, long id = 0)
    {
      lock (obj)
      {
        var number = mark;
        var ticks = (DateTime.Now.Ticks - GuidInt).ToString();
        int fillCount = 0;//填充位数

        number += GetTimeStr(timeType, out fillCount);
        if (id > 0)
        {
          number += ticks.Substring(ticks.Length - fillCount) + id.ToString().PadLeft(19, '0');
        }
        else
        {
          number += GuidIntStr.PadLeft(10, '0') + ticks.Substring(ticks.Length - (9 + fillCount));
        }
        return number;
      }
    }

    /// <summary>
    /// 获取时间字符串
    /// </summary>
    /// <param name="timeType">时间精确类型 1 日,2 时,3 分，4 秒(默认)</param>
    /// <param name="fillCount">填充位数</param>
    /// <returns></returns>
    private static string GetTimeStr(int timeType, out int fillCount)
    {
      var time = DateTime.Now;
      if (timeType == 1)
      {
        fillCount = 6;
        return time.ToString("yyyyMMdd");
      }
      else if (timeType == 2)
      {
        fillCount = 4;
        return time.ToString("yyyyMMddHH");
      }
      else if (timeType == 3)
      {
        fillCount = 2;
        return time.ToString("yyyyMMddHHmm");
      }
      else
      {
        fillCount = 0;
        return time.ToString("yyyyMMddHHmmss");
      }
    }
  }