How to prevent a combobox from closing after a selection is clicked?

I've got a combobox and it's populated with a bunch of checkboxes. I wish the user to be able to click multiple times before the combobox closes (or is closed by the user themselves). The problems right now is that each time a checkbox is clicked, the combobox closes, forcing the user who wants to select multiple options to re-open it several times.

I've found other questions on the same subject but those apply to Silverlight, Qt etc. comparing the tags.

I've tried setting StayOpenOnEdit but that didn't do the trick. As far I could see, there's no property addressing my issue. That creates a suspicion that I might be barning up the wrong component all together.

1. How do I prevent the combobox to close automatically after a click in a checkbox in it?


2. Is there a more suitable component for such task and, if so, what's its name?

Please note that even if the answer to #2 is "yes", I'm still curious of #1 for purely academic reasons.

The point is to achieve something like this but it needs to be a standard WPF control (the concatenated line of all selected items is nice but not a must). Also, I've read the complaints that the binding and handling is not fully developed yet and I feel a bit suspicious.