Create Event Handler for TreeViewItem in WPF

Question

Im adding items to TreeView control via ItemsSource property and ItemTemplate property to set the template for TreeViewItem. How can i add an event handler to handle selection change event on TreeViewItems?
For now my ItemTemplate looks like this:

<Window.Resources><DataTemplate x:Key="PeerDetailTemplate">
        <TextBlock Text="{Binding DESCRIPTION}" Tag="{Binding ID}" GotFocus="GetModules"/>
</DataTemplate></Window.Resources>

But it doesnt work (GetModules is not called). Im new to WPF, so show me the right direction to do such things, please.

Answer 1

You'll need to add an event handler to the TreeView's SelectedItemChanged event.

<TreeView x:Name="myTreeView"
          SelectedItemChanged="myTreeView_SelectedItemChanged"
          ItemTemplate="{StaticResource PeerDetailTemplate} />

Since this is fired after the selection is changed, you can use the TreeView's selected item property to access the tree view item:

private void myTreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
    {
        TreeViewItem selectedItem = (TreeViewItem)myTreeView.SelectedItem;
        // do stuff
    }

Answer 2

If you want to capture the SelectedItemChanged event in a TreeView, then you need to set the event handler on the parent node, i.e.,

XAML

<StackPanel>
    <TreeView SelectedItemChanged="OnTreeViewSelectedItemChanged">          
        <TreeViewItem Header="Desktop">
            <TreeViewItem Header="Computer" />
            <TreeViewItem Header="My Documents" />
            <TreeViewItem Header="c:\" />
        </TreeViewItem>
        <TreeViewItem Header="Recyle Bin" >
            <TreeViewItem Header="foo.txt" />
            <TreeViewItem Header="bar.txt" />
            <TreeViewItem Header="fizz.buzz" />
        </TreeViewItem>
        <TreeViewItem Header="Control Panel" >
            <TreeViewItem Header="Programs" />
            <TreeViewItem Header="Security" />
            <TreeViewItem Header="User Accounts" />
        </TreeViewItem>
    </TreeView>

    <TextBlock Margin="20" x:Name="MyTextBlock" />
</StackPanel>

Code Behind:

private void OnTreeViewSelectedItemChanged( object sender, RoutedPropertyChangedEventArgs<object> e )
{
    MyTextBlock.Text = ( (TreeViewItem) ( (TreeView) sender ).SelectedItem ).Header.ToString();
}

Answer 3

Selection and Selection and focus are two different concepts. It sounds like you're interested in selection, which in this case is a property of the TreeView. Event TreeView.SelectedItemChanged will notify you of selection changes and property TreeView.SelectedItem will tell you what is selected.