C# wrapper around MSDelta's ApplyDeltaB API

Delta.cs

class Delta
{
    [StructLayout(LayoutKind.Sequential)]
    private struct DELTA_INPUT
    {
        public IntPtr lpcStart;
        public UIntPtr uSize;
        [MarshalAs(UnmanagedType.Bool)]
        public bool Editable;
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct DELTA_OUTPUT
    {
        public IntPtr lpcStart;
        public UIntPtr uSize;
    }

    [Flags]
    private enum DELTA_FLAG_TYPE : long
    {
        None = 0,
        AllowPa19 = 1
    }

    [DllImport("msdelta.dll", SetLastError = true)]
    private static extern bool ApplyDeltaB(DELTA_FLAG_TYPE ApplyFlags, DELTA_INPUT Source, DELTA_INPUT Delta, out DELTA_OUTPUT lpTarget);

    [DllImport("msdelta.dll", SetLastError = true)]
    private static extern bool DeltaFree(IntPtr lpMemory);

    static public byte[] ApplyDelta(byte[] Orig, byte[] Delta)
    {
        DELTA_INPUT hOrig = new DELTA_INPUT() { lpcStart = IntPtr.Zero, uSize = new UIntPtr((uint)Orig.Length), Editable = true },
            hDelta = new DELTA_INPUT() { lpcStart = IntPtr.Zero, uSize = new UIntPtr((uint)Delta.Length), Editable = true };
        DELTA_OUTPUT hResult = new DELTA_OUTPUT() { lpcStart = IntPtr.Zero, uSize = UIntPtr.Zero };

        try
        {
            hOrig.lpcStart = Marshal.AllocHGlobal(Orig.Length);
            Marshal.Copy(Orig, 0, hOrig.lpcStart, Orig.Length);

            hDelta.lpcStart = Marshal.AllocHGlobal(Delta.Length);
            Marshal.Copy(Delta, 0, hDelta.lpcStart, Delta.Length);

            if (!ApplyDeltaB(DELTA_FLAG_TYPE.AllowPa19, hOrig, hDelta, out hResult))
                throw new Win32Exception(Marshal.GetLastWin32Error());
            byte[] Result = new byte[hResult.uSize.ToUInt32()];
            Marshal.Copy(hResult.lpcStart, Result, 0, Result.Length);
            return Result;
        }
        finally
        {
            if (hOrig.lpcStart != IntPtr.Zero)
                Marshal.FreeHGlobal(hOrig.lpcStart);
            if (hDelta.lpcStart != IntPtr.Zero)
                Marshal.FreeHGlobal(hDelta.lpcStart);
            if (hResult.lpcStart != IntPtr.Zero)
                DeltaFree(hResult.lpcStart);
        }
    }
}

Companion gist to https://rathertech.blogspot.com/2019/10/select-from-tfvc.html

The API is documented at https://docs.microsoft.com/en-us/previous-versions/bb417345(v=msdn.10)