By default, the ExpandOnSearch property is False. The IncrementalSearch property specifies the control's incremental searching type. If the ExpandOnSearch property is True, and user starts typing characters within the control, it takes each item, if the item is not found but it has child items, it expands the item, and start looking inside the child items, and so on. The property has effect only if the items display child items. When using the ExpandOnSearch property you have to be carefully that your browsed object does not provide recursive objects. In other words, an object that returns an already browsed object and so on. Use the ExpandItem property to programmatically expand/collapse an item. Use the ExpandAll method to expand all items.