>>>>I have a form with combo box. If the user double clicks a list item and it happens to be over another control, the other control gets clicked.
>>>>
>>>>How can this be prevented?
>>>
>>>By the user. Educate the user by telling that an item is selected by a single click.
>>
>>I have found that relying on educating the user is (1) a frustrating and usually fruitless exercise, and (2) a poor substitute for better software operating design.
>
>I fully understand your point. But nevertheless, these double-clicking users will eventually learn that it really is one click too much on that screen. So, the developer can best totally ignore the complaint and reply: "It is by design".

Disagree totally.