This C# code successfully gets the 2 relevant records into _currentUserRegisteredEventIds:

ctx.FetchEventsForWhichCurrentUserIsRegistered((op) =>
            {
                if (!op.HasError)
                {
                    var items = op.Value;
                    _currentUserRegisteredEventIds = new HashSet<int>(items);
                    UpdateRegistrationButtons();
                }
            }, null);

but VB code trying to do the same thing has nothing in _currentUserRegisteredEventIds:

ctx.FetchEventsForWhichCurrentUserIsRegistered(Function(op)
If Not op.HasError Then
    Dim items = op.Value
   _currentUserRegisteredEventIds = New HashSet(Of Integer)(items)
    UpdateRegistrationButtons()
End If

Any help appreciated.