TreeView should look something like this: -Item1 (class A) We get asked about them pretty frequently.How to write XAML for WPF TreeView so when I bind ViewModel with following structure? public class A It's possible we may some day choose to extend binding functionality When the target property is not a DP or the DP is read-only, there's We store in the EffectiveValueTable for the target DependencyObject. Per-instance state of a binding is held in a BindingExpression, which We cannot do this in WPF today, for the same reason we cannot supportīindings on properties that are not DependencyProperties. See edit.Įdit: Looks like this is a bug or "by design" behavior from Microsoft, according to this question there are some workarounds posted, though. This is, of course, assuming that you implement INotifyPropert圜hanged on that particular property. Now you can bind the selected item, and also set it in your view model to change it programmatically, should that requirement ever arise. TreeViewItem item = (TreeViewItem)(p) Īdd the namespace declaration containing that class to your XAML and bind as follows (local is how I named the namespace declaration): Internal void ChangeSelectedItem(object p) View.SelectedItemChanged += (sender, e) => SetSelectedItem(view, e.NewValue) Public TreeViewSelectedItemBehavior(TreeView view) Private class TreeViewSelectedItemBehavior TreeViewSelectedItemBehavior view = behaviors Private static void SelectedItemChanged(DependencyObject obj, DependencyPropert圜hangedEventArgs e)īehaviors.Add(obj, new TreeViewSelectedItemBehavior(obj as TreeView)) Public static readonly DependencyProperty SelectedItemProperty =ĭependencyProperty.RegisterAttached("SelectedItem", typeof(object), typeof(TreeViewHelper), new UIPropertyMetadata(null, SelectedItemChanged)) This enables animation, styling, binding, etc. Using a DependencyProperty as the backing store for SelectedItem. Obj.SetValue(SelectedItemProperty, value) Public static void SetSelectedItem(DependencyObject obj, object value)
Return (object)obj.GetValue(SelectedItemProperty) Public static object GetSelectedItem(DependencyObject obj) Private static Dictionary behaviors = new Dictionary() You can create an attached property that is bindable and has a getter and setter: public class TreeViewHelper RaisePropert圜hanged(() => SelectedObject) ViewModel: public object SelectedObject // Class is not actually "object" Listen to the SelectedItemChanged in TreeView, and add a handler in code-behind to set your ContentControl.Content to the newly selected item.Ĭode Behind: private void TreeView_SelectedItemChanged(object sender, RoutedPropert圜hangedEventArgs e).This ContentControl will "hold" the selected object and handle it's binding, OneWayToSource Name it appropriately, and bind its Content to some SelectedSomething property in viewmodel. Create a visibility-collapsed ContentControl on the same View the TreeView is.Handler(this, new Propert圜hangedEventArgs(propertyName)) Ī very unusual but quite effective way to solve this in a MVVM-acceptable way is the following: Protected virtual void OnPropert圜hanged(string propertyName) Public event Propert圜hangedEventHandler Propert圜hanged Static virtual void OnSelectedItemChanged() otherwise there will be conflicts for more than one tree. Also this should be moved to an instance property on a VM for the whole tree, This is public get-only here but you could implement a public setter which Private static object _selectedItem = null Public class TViewModel : INotifyPropert圜hanged You should not really need to deal with the SelectedItem property directly, bind IsSelected to a property on your viewmodel and keep track of the selected item there.
#WPF TREEVIEW HOW TO#
It says "unknown error system.windows has not been preloaded" and I haven't yet figured out how to get past that.įor Bonus Points: why the hell did Microsoft make this element's SelectedItem property ReadOnly? I have seen this question, but using the answer given gives me compile errors, for some reason I cannot add a reference to the blend sdk to my project. Several other questions are asked about this, but no other working solutions are given.
This is the only solution I have found, but it is an obvious hack, it creates another element in XAML that uses ElementName binding to set itself to the treeviews selected item, which you must then bind your Viewmodel too. I am using MVVM, so there is no codebehind or variable to reference the treeview by. I just need to know what item is selected. I have the TreeView populating, even updating when it's databound collection changes. The TreeView in WPF doesn't allow you to set the SelectedItem, saying that the property is ReadOnly.
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