How to generate absolutely unique GUID's?

Question

Is there a way to generate every time a 100% new GUID without any chance to collide within entire application?

Since I cannot answer my question in eight hours, I come up with the solution:

internal static class GuidGenerator
{
    private static readonly HashSet<Guid> _guids = new HashSet<Guid>();

    internal static Guid GetOne()
    {
        Guid result;

        lock (_guids)
            while (!_guids.Add(result = Guid.NewGuid())) ;

        return result;
    }
    internal static void Utilize(Guid guid)
    {
        lock (_guids)
            _guids.Remove(guid);
    }
}

Is this code solves the problem within the app?

EDIT: Uh, its getting complicated. Thread safety kills the speed.

Answer 1

No, there isn't any way to generate absolutely unique GUIDs. There are only 3.40282367 × 10³⁸ possible GUIDs so as galaxies collide so will these identifiers. Even for a single application, it depends on how many GUIDs the application has. Unless your app is bigger than all of Google's indexers combined, you don't need to lose sleep over this. Just use Guid.NewGuid().