How to close a dropdownlist on mouse leave

I reckon your best bet would be to dynamically select something else on mouse leave of the dropdown. Thus setting the focus to something else. closing your dropdown.

comboBox1.DroppedDown = false;
does close the drop down list as you might expect.

The problem is that combo1_MouseLeave (event) does not fire when the mouse leaves, if the drop down is dropped. I also investigated MouseMouse. It also does not fire while the drop down is dropped.

I seem to remember having this problem in VB6. The drop down is managed by the system. This allows the drop down to drop outside the limits of the host window and on top of other applications, until it is closed, but means the application has little visibility into any events that happen while dropped down.