title: wpf - autocompletebox doesn't update on mousedown
body: <p>I have an autocompletebox that works but for one oddity I was hoping for help with. When selecting an item in the popup, using the keyboard to arrow down and then selecting it using either the enter key or with the mouse, the item is selected and updated into the autocompletebox. However, if one instead of arrowing down to the item simply hovers over it instead and select it with the mouse, the selecteditem is set correctly but the autocompletebox doesn't get updated with the selecteditem.</p>
  
  <p>That is, arrow down and select an item and the autocompletebox reflects the selected item whereas just hovering over and selecting the item means the autocompletebox does not reflect the selection - instead it shows what the user typed into the box; note that the backing property is aware of the selected item so it does work either way, only it's not reflected in the textbox.</p>
  
  <p>Any help is appreciated.
  Thanks</p>
  
  <p>I should add that it is OnSelectedItemChanged that doesn't seem to get called...</p>