protected override void OnItemsSourceChanged(OldNew <IEnumerable> input) { base.OnItemsSourceChanged(input); if (TreeViewExtensions.GetMode(treeView) == TreeViewModes.Grid) { var columns = TreeViewExtensions.GetColumns(treeView); if (columns?.Count > 0) { columns.ForEach(i => { if (!DependencyObjectExtensions.GetIsVisible(i)) { Hide(i); } }); } } }