创建有序的guid

    public static class API
    {
        /// <summary>
        /// 创建有序的 guid。
        /// </summary>
        /// <returns></returns>
        public static Guid NewSequentialGuid()
        {
            Guid result;
            UuidCreateSequential(out result);
            return result;
        }

        /// <summary>
        /// http://stackoverflow.com/questions/211498/is-there-a-net-equalent-to-sql-servers-newsequentialid
        /// </summary>
        /// <param name="guid"></param>
        /// <returns></returns>
        [DllImport("rpcrt4.dll", SetLastError = true)]
        private static extern int UuidCreateSequential(out Guid guid);


        [Obsolete("这个不是有序的，测试未通过。")]
        /// <summary>
        /// http://snipplr.com/view.php?codeview&id=29304
        /// </summary>
        /// <returns></returns>
        public static Guid NewComb()
        {
            byte[] dateBytes = BitConverter.GetBytes(DateTime.Now.Ticks);
            byte[] guidBytes = Guid.NewGuid().ToByteArray();
            // copy the last six bytes from the date to the last six bytes of the GUID
            Array.Copy(dateBytes, dateBytes.Length - 7, guidBytes, guidBytes.Length - 7, 6);
            return new Guid(guidBytes);
        }
    }

　　测试

    [TestFixture]
    public class APITest
    {
        [Test]
        public void testUuidCreateSequential()
        {
            List<Guid> list = new List<Guid>();
            for (int i = 0; i < 100; i++)
            {
                Guid id = API.NewSequentialGuid();
                list.Add(id);
                Console.WriteLine(id);
            }
            for (int i = 0; i < list.Count - 1; i++)
            {
                Assert.Less(list[i], list[i + 1]);
            }
        }

        [Test]
        public void testNewComb()
        {
            List<Guid> list = new List<Guid>();
            for (int i = 0; i < 100; i++)
            {
                Guid id = API.NewComb();
                list.Add(id);
                Console.WriteLine(id);
            }
            for (int i = 0; i < list.Count - 1; i++)
            {
                Assert.Less(list[i], list[i + 1]);
            }

        }
    }