C#实现SQLSERVER数据库中有序GUID生成（NewSequentialId）

GUID作为数据库主键由于其无序性所以性能不怎么好，SQL Server中有个函数NewSequentialId可以生成有序的GUID，由于在程序中需要用到，就用C#实现了一下，生成的GUID格式基本和SQL Server一致。

程序代码参考了rpcrt4.dll中UuidCreateSequential的实现。

    public class GuidHelper
    {
        private static bool initialised;
        private static int count;

        private static long time;
        private static long timelast;
        private static ushort sequence;

        private static byte[] address; //网卡MAC
        private static readonly object locker = new object();
        public static Guid NewSequentialId()
        {
            lock(locker)
            {
                if (!initialised)
                {
                    timelast = UuidGetSystemTime();
                    count = TICKS_PER_CLOCK_TICK;
                    Random rand = new Random(1);
                    sequence = (ushort)(((rand.Next(1, 32767) & 0xFF) << 8) + rand.Next(1, 32767) & 0xFF);
                    sequence &= 0x1FFF;
                    address = GetAddressBytes();
                    initialised = true;
                }
                while (true)
                {
                    time = UuidGetSystemTime();
                    if (time > timelast)
                    {
                        count = 0;
                        break;
                    }
                    if (time < timelast)
                    {
                        sequence = (ushort)((sequence + 1) & 0x1FFF);
                        count = 0;
                        break;
                    }
                    if (count < TICKS_PER_CLOCK_TICK)
                    {
                        count++;
                        break;
                    }
                }

                timelast = time;
                time += count;

                byte[] guidArray = new byte[16];

                uint data1 = (uint)(time & 0xffffffff);
                ushort data2 = (ushort)((time >> 32) & 0xffff);
                ushort data3 = (ushort)((time >> 48) & 0x0fff);
                /* This is a version 1 UUID */
                data3 |= (1 << 12);

                guidArray[3] = (byte)data1;
                guidArray[2] = (byte)(data1 >> 8);
                guidArray[1] = (byte)(data1 >> 16);
                guidArray[0] = (byte)(data1 >> 24);
                guidArray[5] = (byte)data2;
                guidArray[4] = (byte)(data2 >> 8);
                guidArray[7] = (byte)data3;
                guidArray[6] = (byte)(data3 >> 8);
                guidArray[8] = (byte)(sequence & 0xff);
                guidArray[9] = (byte)((sequence & 0x3f00) >> 8);
                guidArray[9] |= 0x80;
                Array.Copy(address, 0, guidArray, 10, 6);

                return new Guid(guidArray);
            }//locker
        }//UuidCreateSequential

        private static readonly int TICKS_PER_CLOCK_TICK = 1000;
        private static readonly int SECSPERDAY = 86400;
        private static readonly int TICKSPERSEC = 10000000;
        private static readonly long SECS_15_OCT_1582_TO_1601 = (17 + 30 + 31 + 365 * 18 + 5) * SECSPERDAY;
        private static readonly long TICKS_15_OCT_1582_TO_1601 = SECS_15_OCT_1582_TO_1601 * TICKSPERSEC;
        private static long UuidGetSystemTime()
        {
            DateTime dt = DateTime.Now;
            var ft = dt.ToFileTime();
            ft += TICKS_15_OCT_1582_TO_1601;
            return ft;
        }

        private static byte[] GetAddressBytes()
        {
            byte[] bytes;
            NetworkInterface[] nic = NetworkInterface.GetAllNetworkInterfaces();
            if (nic == null || nic.Length < 1)
            {
                bytes = new byte[6];
                bytes[0] = 0x01;
                return bytes;
            }
            bytes = nic[0].GetPhysicalAddress().GetAddressBytes();
            return bytes;
        }
    }

代码写的比较粗糙，不过功能已经实现，有需要的朋友可以自行优化！