protected override void HandleKeyDown( object sender, KeyEventArgs e )
{
// The base call will handle the Ctrl+Down, Enter and Esc keys
// in order to open o r close the popup.
//Do not close the Calendar if the call is handled
//by the TimePicker inside the DateTimePicker template
if( IsOpen
&& _timePicker.IsKeyboardFocusWithin
&& ( _timePicker.IsOpen || e.Handled ) )
return;
base.HandleKeyDown( sender, e );
}