public StoryFrameBuildControlViewModel()
{
_storyFrameModelCollection = new ObservableCollection<IMarkable>();
_selectingIndex = -1;
EventAggregator.AddIMarkableHandler += AddIMarkableHandler;
EventAggregator.DeleteIMarkableHandler += DeleteIMarkableHandler;
EventAggregator.SelectObjectForceHandler += EventAggregator_SelectObjectForceHandler;
}