WPF expand TreeView on single mouse click

Question

I have a WPF TreeView with a HierarchicalDataTemplate.

Currently I have to double click an item to expand/collapse it.

I would like to change this behaviour to a single click, without loosing other functionality. So it should expand and collapse on click.

What is the recommended way to do this?

Thanks!

Answer 1

You could use a re-templated checkbox as your node (containing whatever template you are currently using) with its IsChecked property bound to the IsExpanded property of the TreeViewItem.

Here is a template I've just test that seems to do the job:

<HierarchicalDataTemplate ItemsSource="{Binding Items}">
    <CheckBox IsChecked="{Binding RelativeSource={RelativeSource AncestorType=TreeViewItem}, Path=IsExpanded}">
        <CheckBox.Template>
            <ControlTemplate>
                <TextBlock Text="{Binding Header}"></TextBlock>
            </ControlTemplate>
        </CheckBox.Template>
    </CheckBox>
</HierarchicalDataTemplate>

Just replace the ControlTemplate contents with whatever you need.

Answer 2

If you are using a standard TreeViewItem, then you can capture the click event:

private void OnTreeViewMouseUp( object sender, MouseButtonEventArgs e )
{
    var tv = sender as TreeView;
    var item = tv.SelectedItem as TreeViewItem;

    if( item != null )
        item.IsExpanded = !item.IsExpanded;

    e.Handled = true;
}

private void OnTreeViewPreviewMouseDoubleClick( object sender, MouseButtonEventArgs e )
{
    e.Handled = true;
}

Most likely in your case, you'll need to do something with your binding and ViewModel. Here's a good article from CodePlex: Simplifying the WPF TreeView by Using the ViewModel Pattern.