New Post: [Version 2.0] NullRef when setting IsSelected for Document

     /// <summary>
        /// Provides derived classes an opportunity to handle changes to the IsSelected property.
        /// </summary>
        protected virtual void OnIsSelectedChanged(DependencyPropertyChangedEventArgs e)
        {
            if (_isSelectedReentrantFlag.CanEnter)
            {
                using (_isSelectedReentrantFlag.Enter())
                {
                    LayoutElement.IsSelected = (bool)e.NewValue;
                }
            }
        }