WPF DataBound treeview expand / collapse

Question

I'm just trying to find a way to control the expand / collapse of the TreeView nodes through the object they're bound to. The object has an IsExpanded property, and I want to use that to show the TreeView node itself expanded or collapsed based on that property.

Here's my code:

C#:

public partial class Window2 : Window {     public Window2()     {         InitializeComponent();          this.DataContext = new List<Parent>() { Base.GetParent("Parent 1"), Base.GetParent("Parent 2") };     } }  public class Base {     public string Name { get; set; }     public bool IsExpanded { get; set; }      public static Parent GetParent(string name)     {         Parent p = new Parent() { Name = name };          p.Children.Add(new Child() { Name = "Child 1", GrandChildren = new ObservableCollection<GrandChild>() { new GrandChild() { Name = "Grandchild 1" } } });         p.Children.Add(new Child() { Name = "Child 2", GrandChildren = new ObservableCollection<GrandChild>() { new GrandChild() { Name = "Grandchild 1" } } });         p.Children.Add(new Child() { Name = "Child 3", GrandChildren = new ObservableCollection<GrandChild>() { new GrandChild() { Name = "Grandchild 1" } } });          return p;     } }  public class Parent : Base {     public ObservableCollection<Child> Children { get; set; }      public Parent()     {         this.Children = new ObservableCollection<Child>();     } }  public class Child : Base {     public ObservableCollection<GrandChild> GrandChildren { get; set; }      public Child()     {         this.GrandChildren = new ObservableCollection<GrandChild>();     } }  public class GrandChild : Base { } 

XAML:

<Window x:Class="HeterogeneousExperimentExplorer.Window2"     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"         xmlns:local="clr-namespace:HeterogeneousTree"     Title="Window2" Height="300" Width="300">     <Window.Resources>         <HierarchicalDataTemplate DataType="{x:Type local:Parent}" ItemsSource="{Binding Children}">             <TextBlock Text="{Binding Name}" />             <HierarchicalDataTemplate.ItemTemplate>                 <HierarchicalDataTemplate DataType="{x:Type local:Parent}" ItemsSource="{Binding GrandChildren}">                     <TextBlock Text="{Binding Name}" />                     <HierarchicalDataTemplate.ItemTemplate>                         <DataTemplate>                             <TextBlock Text="{Binding Name}" />                         </DataTemplate>                     </HierarchicalDataTemplate.ItemTemplate>                 </HierarchicalDataTemplate>             </HierarchicalDataTemplate.ItemTemplate>         </HierarchicalDataTemplate>     </Window.Resources>     <Grid>         <TreeView ItemsSource="{Binding}" />     </Grid> </Window> 

Answer 1

Came up with solution:

<Style TargetType="{x:Type TreeViewItem}">     <Setter Property="IsExpanded" Value="{Binding IsNodeExpanded}"/> </Style> 

So the style gets the object bound to the TreeViewItem and looks at its IsNodeExpanded attribute and it assigns that value to the TreeViewItem.IsExpanded property. If you add Mode=TwoWay, they'll notify each other (TreeViewItem will tell the object when it has been expanded).