![]() When SelectedItem is changed from the view model, the behavior traverses the hierarchy while utilizing HierarchyPredicate to find the correct node, ultimately selecting it. You can attach this behavior to a tree view like this: This goes through all of the tree view's children and in turn calls UpdateTreeViewItem(.) on them. It also calls UpdateAllTreeViewItems() after attaching. To ensure maximum compatibility, it extends an existing style if it can find one or creates a new one otherwise. We need to listen to this event to handle nodes that were expanded. Once this behavior is attached, it calls UpdateTreeViewItemStyle() to inject an event handler for Loaded event of ItemContainerStyle. The predicate can help optimize this process. If it's not set, the behavior will just blindly expand all nodes until it finds the item we're looking for. ![]() To make it easier to check if a node is a child of another node, I defined a property called HierarchyPredicate. Here's the behavior I've implemented: public class TreeViewSelectionBehavior : Behavior When one of the nodes we expanded is loaded, it triggers an event, and we start again from the top.If we instead find its parent, expand it so that we can continue the search once it's loaded.If we manage to find it, select it and exit early.When SelectedItem changes, go through all loaded tree nodes and try to locate the target node.Subscribe to Loaded events of all data items using a style.We can, however, subscribe to the Loaded event of each data item, which will trigger once the control has been loaded. I naively assumed that by expanding the node from code, its children's item containers will immediately become available, but this is not the case because that's handled asynchronously. In order to make our target node visible, we need to expand all of its ancestor nodes one by one, starting from the very top. However, if the node is not visible yet, then the container is also not initialized, making the method return null. This in itself can be accomplished by using the (.) method. To access IsSelected and IsExpanded properties I needed to resolve a reference to an instance of TreeViewItem, which is a container that wraps around the data template. I realized that to solve this I would have to traverse the entire hierarchy of tree nodes, but that wasn't the only problem. I solved this problem by writing a small behavior that takes care of this for me. This was a deal-breaker for me because I wanted the tree view to navigate to the newly selected item, even if it wasn't immediately visible. Both of these approaches suffer from the same problem - an item won't get selected if its parents are not yet expanded. I googled the problem and every resource I've found was guiding me into either handling it in code-behind or adding IsSelected property to my model class. ![]() I think there's no point explaining why binding SelectedItem would be useful, so there should be no surprise in my disappointment. Recently I realized that TreeView.SelectedItem property is read-only and unbindable. The longer I work with WPF, the more I notice how many things it's missing.
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