WPF TreeView: Where is the ExpandAll() method

This might help

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

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.

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.