WPF TreeView: Where is the ExpandAll() method

Question

How can I expand all TreeView nodes in WPF? In WinForms there was a ExpandAll() method which does this.

Answer 1

The WPF TreeView class does not have an ExpandAll method. Thus you'd have to loop through the nodes and set their IsExpanded properties to true.

Answer 2

This might help

<TreeView>
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="IsExpanded" Value="True" />
        </Style>
    </TreeView.ItemContainerStyle>
</TreeView>

Answer 3

with XAML Treeview style you must have a property setter like that what wrote above :

In Cs file, write methods like this, in my sample i used a button and my treeview's name is myTV :

private void ExpandAll(ItemsControl items, bool expand)
    {
        foreach (object obj in items.Items)
        {
            ItemsControl childControl = items.ItemContainerGenerator.ContainerFromItem(obj) as ItemsControl;
            if (childControl != null)
            {
                ExpandAll(childControl, expand);
            }
            TreeViewItem item = childControl as TreeViewItem;
            if (item != null)
                item.IsExpanded = true;
        }
    }


    private void btnExpandAll_Click(object sender, RoutedEventArgs e)
    {

        foreach (object item in this.myTV.Items)
        {
            TreeViewItem treeItem = this.myTV.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;
            if (treeItem != null)
                ExpandAll(treeItem, true);
            treeItem.IsExpanded = true;
        }
    }

hope it could help you.

Answer 4

try this

private void btnExpandAll_Click(object sender, RoutedEventArgs e)
{
    foreach(var item in tvES.Items)
    {
        var tvi = item as TreeViewItem;
        if (tvi != null)
            tvi.ExpandSubtree();
    }
}

Answer 5

The answer provided by @Pierre-Olivier is a good one.

Personally, I prefer to use a stack rather than recursion in circumstances such as these where you have no idea how deeply nested the data could be. Even better, it could be provided as an extension function:

public static void ExpandAll(this TreeViewItem treeViewItem, bool isExpanded = true)
{
    var stack = new Stack<TreeViewItem>(treeViewItem.Items.Cast<TreeViewItem>());
    while(stack.Count > 0)
    {
        TreeViewItem item = stack.Pop();

        foreach(var child in item.Items)
        {
            var childContainer = child as TreeViewItem;
            if(childContainer == null)
            {
                childContainer = item.ItemContainerGenerator.ContainerFromItem(child) as TreeViewItem;
            }

            stack.Push(childContainer);
        }

        item.IsExpanded = isExpanded;
    }
}

public static void CollapseAll(this TreeViewItem treeViewItem)
{
    treeViewItem.ExpandAll(false);
}

Answer 6

In addition to user2779123's comment and I know this is long since been answered but I would also suggest that Pierre-Olivier Pignon's code push the treeItem.IsExpanded = true; not only be moved into scope of the null check but by moving it to the ExpandAll procedure as it appears to be written in a format that allows for both expansion and collapsing of the tree structure and moving this to there would add the root nodes to this functionality by design.

As per the below example:

private void ExpandAll(ItemsControl items, bool expand)
{
    items.IsExpanded = expand;
    foreach (object obj in items.Items)
    {
        ItemsControl childControl = items.ItemContainerGenerator.ContainerFromItem(obj) as ItemsControl;
        if (childControl != null)
        {
            ExpandAll(childControl, expand);
        }
        TreeViewItem item = childControl as TreeViewItem;
        if (item != null)
            item.IsExpanded = true;
    }
}


private void btnExpandAll_Click(object sender, RoutedEventArgs e)
{

    foreach (object item in this.myTV.Items)
    {
        TreeViewItem treeItem = this.myTV.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;
        if (treeItem != null)
            ExpandAll(treeItem, true);
    }
}

Answer 7

    /// <summary>
    /// Collapse the TreeView.
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void _collapseTreeView_button_Click(object sender, RoutedEventArgs e)
    {
        _ordersParentChild_TreeView.UpdateLayout();
        if (_ordersParentChild_TreeView.Items.Count > 0)
        {
            var rootTreeViewItem = _ordersParentChild_TreeView.Items[0] as TreeViewItem;
            if (rootTreeViewItem != null)
            {
                rootTreeViewItem.IsExpanded = false;
            }
        }
    }
    /// <summary>
    /// Expand the TreeView.
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void _expandTreeView_button_Click(object sender, RoutedEventArgs e)
    {
        _ordersParentChild_TreeView.UpdateLayout();
        if(_ordersParentChild_TreeView.Items.Count > 0)
        {
            var rootTreeViewItem = _ordersParentChild_TreeView.Items[0] as TreeViewItem;
            if (rootTreeViewItem != null)
            {
                rootTreeViewItem.ExpandSubtree();
            }
        }
    }
}

Answer 8

It's 2022-01-14 now, and I'm using VS2022 with .net6. I believe during 2015~now, MS built a new method named ExpandSubTree(), which can expand not the whole tree but a single TreeViewItem. It makes things easier.

CollapseAll is quite different because only the first layer need to be collapsed.

public static class TreeViewHelper
{
    public static void ExpandAll(this TreeView treeView)
    {
        foreach (var item in treeView.Items)
        {
            if (treeView.ItemContainerGenerator.ContainerFromItem(item) is TreeViewItem treeViewItem)
                treeViewItem.ExpandSubtree();
        }
    }

    public static void CollapseAll(this TreeView treeView)
    {
        foreach (var item in treeView.Items)
        {
            if (treeView.ItemContainerGenerator.ContainerFromItem(item) is TreeViewItem treeViewItem)
                treeViewItem.IsExpanded = false;
        }
    }

    public static void CollapseAll(this TreeViewItem treeViewItem)
    {
        foreach (var item in treeViewItem.Items)
        {
            if (treeViewItem.ItemContainerGenerator.ContainerFromItem(item) is TreeViewItem subTreeViewItem)
                subTreeViewItem.IsExpanded = false;
        }
    }
}