Silverlight TreeView expand all nodes under top node

Question

I am working with a Silverlight TreeView. When the control loads, all the nodes are closed. When I click on one of the nodes I need for all the child nodes under that opened parent node to expand. How do I do this? My experience with TreeView is very limited so example code would really help out a lot. Thanks!

Number8 Number8 · Accepted Answer · 2013-10-30T17:58:12

Attach a handler to each TreeViewItem's Expanded event. Then, traverse the tree of children, expanding each node as you go.

Simple XAML:

        <sdk:TreeView>
        <sdk:TreeViewItem Expanded="TreeViewItem_OnExpanded" Header="One"></sdk:TreeViewItem>
        <sdk:TreeViewItem Expanded="TreeViewItem_OnExpanded" Header="Two">
            <sdk:TreeViewItem Expanded="TreeViewItem_OnExpanded" Header="Three">
                <sdk:TreeViewItem Expanded="TreeViewItem_OnExpanded" Header="Four">
                    <sdk:TreeViewItem Expanded="TreeViewItem_OnExpanded" Header="Five" />
                </sdk:TreeViewItem>
            </sdk:TreeViewItem>
        </sdk:TreeViewItem>
    </sdk:TreeView>

Code behind:

    private void TreeViewItem_OnExpanded(object sender, RoutedEventArgs e)
    {
        TreeViewItem tvi = sender as TreeViewItem;
        Debug.Assert(tvi != null);

        if (tvi.HasItems) { ExpandChildren(tvi); }
    }

    private void ExpandChildren(TreeViewItem tvi)
    {
        foreach (var item in tvi.Items)
        {
            if (item is TreeViewItem) { ExpandChildren(item as TreeViewItem); }
        }
        tvi.IsExpanded = true;
    }

I don't know how to set up an event handler in a TreeView.ItemTemplate, however.
Perhaps another reader knows how to do that ... ?

Silverlight TreeView expand all nodes under top node

1 Answers