using System;
using System.Data.SqlTypes;

public class FunctionNewGuid
{
    [Microsoft.SqlServer.Server.SqlFunction]
    public static SqlGuid NewSequentialGuid()
    {
        const int RPC_S_OK = 0;
        Guid guid;
        int result = UuidCreateSequential(out guid);

        if (result != RPC_S_OK)
        {
            throw new System.ComponentModel.Win32Exception(System.Runtime.InteropServices.Marshal.GetLastWin32Error());
        }
        else
        {
            byte[] guidBytes = guid.ToByteArray();
            Array.Reverse(guidBytes, 0, 4);
            Array.Reverse(guidBytes, 4, 2);
            Array.Reverse(guidBytes, 6, 2);

            long timestamp = DateTime.UtcNow.Ticks / 10000L;
            byte[] timestampBytes = BitConverter.GetBytes(timestamp);

            if (BitConverter.IsLittleEndian)
            {
                Array.Reverse(timestampBytes);
            }
            Buffer.BlockCopy(timestampBytes, 2, guidBytes, 10, 6);
            return new SqlGuid(guidBytes);
        }

    }

    [System.Runtime.InteropServices.DllImport("rpcrt4.dll", SetLastError = true)]
    private static extern int UuidCreateSequential(out Guid guid);
}