WPF tab order with custom controls?

Question

I have a WPF page that contains several out of the box controls with the tab order set.

I have a custom control (NumericSpinner) that contains: border/grid/text box/

Answer 1

I've tried using the selected answer's GotFocus event, but it doesn't work for me, it seems to disable the tab navigation altogether, even though the first TabStop is indeed selected.
What worked for me was using the WindowActivated event and use the same command there:

MoveFocus(new TraversalRequest(FocusNavigationDirection.First));

I hope it might help someone.