ArcGISRuntime.Samples.Desktop.MainWindow.Categories_Click C# (CSharp) Method

        private void Categories_Click(object sender, RoutedEventArgs e)
        {
            if (_openCategoryLeafs)
            {
                _openCategoryLeafs = false;
                if (categories.Items.Count > 0)
                {
                    var firstTreeViewItem = categories.Items[0] as TreeViewItem;
                    firstTreeViewItem.IsSelected = true;

                    foreach (var item in categories.Items)
                    {
                        var treeViewItem = item as TreeViewItem;
                        treeViewItem.IsExpanded = true;
                    }
                }
            }
            featured.Visibility = Visibility.Collapsed;
            categories.Visibility = Visibility.Visible;
        }