Generates sortable sequential GUIDs

Get-SeqGuid.ps1

$c = @"
using System;
using System.Runtime.InteropServices;

public static class SeqGuid {
    private class NativeMethods
    {
       [DllImport("rpcrt4.dll", SetLastError=true)]
       public static extern int UuidCreateSequential(out Guid guid);
    }

    public static Guid NewSequentialID()
    {
       //Code is released into the public domain; no attribution required
       const int RPC_S_OK = 0;

       Guid guid;
       int result = NativeMethods.UuidCreateSequential(out guid);
       if (result != RPC_S_OK)
          return Guid.NewGuid();

       //Endian swap the UInt32, UInt16, and UInt16 into the big-endian order (RFC specified order) that SQL Server expects
       //See https://stackoverflow.com/a/47682820/12597
       //Short version: UuidCreateSequential writes out three numbers in litte, rather than big, endian order
       var s = guid.ToByteArray();
       var t = new byte[16];

       //Endian swap UInt32
       t[3] = s[0];
       t[2] = s[1];
       t[1] = s[2];
       t[0] = s[3];
       //Endian swap UInt16
       t[5] = s[4];
       t[4] = s[5];
       //Endian swap UInt16
       t[7] = s[6];
       t[6] = s[7];
       //The rest are already in the proper order
       t[8] = s[8];
       t[9] = s[9];
       t[10] = s[10];
       t[11] = s[11];
       t[12] = s[12];
       t[13] = s[13];
       t[14] = s[14];
       t[15] = s[15];

       return new Guid(t);
    }
}
"@

$t =  Add-Type -TypeDefinition $c -Language CSharp 

[SeqGuid]::NewSequentialID()