public sealed class SequentialGuid{//使用 Guid.NewGuid() 的字节重排/// <summary>/// 优点及适用场景：/// 1.系统只在应用层生成GUID，追求极致的插入性能和最低的索引碎片/// 2.系统并发量极高，需要最高的时间戳精度来避免冲突（因为使用系统滴答计数（Tick），精度为100纳秒）/// </summary>/// <param name="guidType"></param>/// <returns></returns>public static Guid Create(SequentialGuidType guidType = SequentialGuidType.SequentialAsString){var randomBytes = Guid.NewGuid().ToByteArray();var timeBytes = BitConverter.GetBytes(DateTime.UtcNow.Ticks);if (BitConverter.IsLittleEndian)Array.Reverse(timeBytes);byte[] sequentialBytes;switch (guidType){case SequentialGuidType.SequentialAsString:case SequentialGuidType.SequentialAsBinary:sequentialBytes = new byte[16];Buffer.BlockCopy(timeBytes, 2, sequentialBytes, 0, 6);Buffer.BlockCopy(randomBytes, 0, sequentialBytes, 6, 10);break;case SequentialGuidType.SequentialAtEnd:sequentialBytes = new byte[16];Buffer.BlockCopy(randomBytes, 0, sequentialBytes, 0, 10);Buffer.BlockCopy(timeBytes, 2, sequentialBytes, 10, 6);break;default:throw new ArgumentOutOfRangeException("guidType");}return new Guid(sequentialBytes);}public enum SequentialGuidType{SequentialAsString,SequentialAsBinary,SequentialAtEnd}//使用 Comb GUID 算法/// <summary>/// 优点及适用场景：/// 1.需要与SQL Server NEWSEQUENTIALID() 完全兼容和互操作/// 2.简单、稳定、社区接受度高 /// 3.精度较低（约3.33毫秒）。/// PS：建议使用此方案/// </summary>/// <returns></returns>public static Guid NewComb(){byte[] guidArray = Guid.NewGuid().ToByteArray();DateTime baseDate = new DateTime(1900, 1, 1);DateTime now = DateTime.Now;// 获取从基准时间到现在的毫秒数TimeSpan days = new TimeSpan(now.Ticks - baseDate.Ticks);TimeSpan msecs = now.TimeOfDay;// 转换为字节数组byte[] daysArray = BitConverter.GetBytes(days.Days);byte[] msecsArray = BitConverter.GetBytes((long)(msecs.TotalMilliseconds / 3.333333));// 反转字节顺序，因为 .NET 是小端序if (BitConverter.IsLittleEndian){Array.Reverse(daysArray);Array.Reverse(msecsArray);}// 将时间部分复制到 GUID 中Buffer.BlockCopy(daysArray, daysArray.Length - 2, guidArray, guidArray.Length - 6, 2);Buffer.BlockCopy(msecsArray, msecsArray.Length - 4, guidArray, guidArray.Length - 4, 4);return new Guid(guidArray);}//使用 MassTransit 的有序 GUID/// <summary>/// NewId 转换为 GUID 可能不符合 RFC 4122 标准/// 高性能要求：选择 MassTransit NewId/// </summary>/// <returns></returns>public static Guid MassGenGuid(){return MassTransit.NewId.Next().ToGuid();// 或者直接使用 NewId 类型// Id = NewId.Next().ToString()
}}
