![]() SetTreeViewSelectedItem(( DependencyObject )sender, e.Synchronizing a SelectedPath property with the SelectedItem in WPFs TreeView. Need a sample for WPF TreeView search with Virtualization and Load On Demand. static void tv_SelectedItemChanged( object sender, RoutedPropertåhangedEventArgs e) How is it possible to programmatically select an item in a WPF TreeView The ItemsControl model seems to prevent it.// When TreeView.SelectedItemChanged fires, set our new property to the value.new RoutedPropertåhangedEventHandler (tv_SelectedItemChanged).TreeView tv = dependencyObject as TreeView.private static void TreeViewSelectedItemChanged( DependencyObject dependencyObject,.// for the TreeView's SelectedItemChanged event.// When our property is set to a non null value we need to add an event handler.// This is the handler for when our new property's value changes.SetValue(TreeViewSelectedItemProperty, value) DependencyObject dependencyObject, object value).public static void SetTreeViewSelectedItem(.// As well as a Set method for our new property.public static object GetTreeViewSelectedItem( DependencyObject dependencyObject).// We need a Get method for our new property.new PropertåhangedCallback (TreeViewSelectedItemChanged))).new FrameworkPropertyMetadata ( null, FrameworkPropertyMetadataOptions.typeof ( TreeViewSelectedItemBehaviour ),.public static readonly DependencyProperty TreeViewSelectedItemProperty =.// we can bind to it from oout ViewMode.// Declare our attached property, it needs to be a DependencyProperty so.public class TreeViewSelectedItemBehaviour. Here's the code for our attached property you set ItemTemplate for TreeViewItem, but you should set ItemTemplate for TreeView you added inside instead of you should bind to ItemsSource of TreeView with your main collection and to ItemsSource of HierarchicalDataTemplate with collection inside each element.When this event is fired we set the value of our attached property to the value of the SelectedItem and this automatically updates our ViewModel. The clever part happens within our property implementation, here is where we subscribe to the TreeView.SelectedItemChanged event. ![]() We can then bind to this property from our ViewModel. ![]() The basic principle behind this technique is we define a custom property that we can attach to our TreeView in XAML. I'm sure you will see more of these in my future posts. Defining custom attached properties is a handy technique for MVVM that allows us to bind properties of a ViewModel to otherwise inaccessible parts of our View such as read-only properties and events. So how can we access the selected item from our ViewModel? The answer is with an attached property. That's because the WPF TreeView's SelectedItem property is read-only so we can't set the binding in XAML like normal. At first, binding to the TreeView's SelectedItem property sounds like a simple task, but if you give it a go you will soon realise it's not so straight forward. ![]()
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