How to show parent nodes during filtering when at least one child nodes meets an applied filter

By default, if a child node meets filter criteria but the parent node doesn't, the parent node is hidden. To change this behavior, it is necessary to handle the CustomNodeFilter event and implement filtering logic manually. To check whether or not a node meets filter criteria, use the ExpressionEvaluator.Fit method.

In addition, if the HierarchicalDataTemplate mode is used, the TreeListView creates child nodes only when you expand a parent node for the first time. So, the required step in this scenario is to expand all nodes to forcibly create them.