Question

I try to have a treeview that browse potentially cyclic hierarchical data.
This means that I cannot try to load all the tree at once, since there maybe be infinite loops then.

I would like to react to the TreeView.AfterCollapse Event documented here at MSDN

however, my control doesnt seem to have this event. If I try to add the AfterExpand attribute, i get this error message:

 error MC3072: The property 'AfterExpand' does not exist in XML namespace 'http://schemas.microsoft.com/winfx/2006/xaml/presentation'. Line 23 Position 21.

What I am doing wrong ? Calling a wrong namespace ?
Here is the code:

<Window x:Class="MyApp.Edit.EditView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:MyApp.Edit"
    Title="{Binding WindowTitle,UpdateSourceTrigger=PropertyChanged}" MinHeight="350" MinWidth="350">

    <Window.Resources>
        <HierarchicalDataTemplate x:Key="sectionTemplate"
        ItemsSource="{Binding ChildSections}"
        DataType="{x:Type local:Section}">
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding Label, UpdateSourceTrigger=PropertyChanged}" />
                <TextBlock Text=" - " />
                <TextBlock Text="{Binding Description}" FontStyle="Italic" Foreground="#777" />
            </StackPanel>
        </HierarchicalDataTemplate>
    </Window.Resources>

    <StackPanel>

    <TreeView ItemsSource="{Binding Sections}"
                SelectedItemChanged="TreeView_SelectedItemChanged"
                ItemTemplate="{StaticResource sectionTemplate}"
                MinHeight="150"
                MinWidth="300"
                Name="treeView"
                AfterExpand="MyEventHandler"
        </TreeView>

        <TextBox Text="{Binding Label, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" 
                 Margin="0 10 0 0"/>

        <TextBox Text="{Binding Description, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" 
                 Margin="0 10 0 0"/>

        <StackPanel Orientation="Horizontal">
            <Button Content="Add Child" Click="Button_Click_AddChild" />
        </StackPanel>
    </StackPanel>
</Window>

Answer 1

That is a Windows Forms tree view event, it does not belong to the WPF TreeView, in WPF you can use Collapsed and Expanded of the TreeViewItems, not the TreeView itself.

However you can subscribe to the events on the TreeView as they are routed.