protected override void OnClick() {
if (_isOpen)
return;
_overview = new OverviewWindow();
_overview.ViewContent = MapControlContentFactory.Create(
MapView.Active.Map, MapView.Active.Extent, MapView.Active.ViewingMode);
_overview.Closed += (s, e) => {
_isOpen = false;
lock (_lock) {
_overview = null;
}
};
_overview.Show();
_isOpen = true;
}