title: How does a ComboBox capture mouse when it is dropped-down?
body: <p>I am trying to model the behavior of a ComboBox dropdown (or other drop downs for that matter, including context menus) where the drop down closes when you click anywhere else, even on something that can't be focused.</p>
  
  <p>I've tried subscribing for events such as MouseCaptureChanged, LostFocus, and Leave.  I have a custom UserControl which is acting as a dropdown and I just want to close it up when the user clicks anywhere else.</p>
  
  <p>This seems like something that's done in many controls so I'd be surprised if there wasn't a simple way to do it.</p>
  
  <p>So far the overcomplicated methods I can come up with to do this are using pinvoke and the SetCapture() function, or to create a MessageFilter.  If these are the only options I am not sure which is better.</p>