Exapned all the nodes of WPF treeView after databinding

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C#

WPF

C#4.0

How we can expend all the nodes of WPF treeview once i have bound it to object. I have used code below

for (int i = 0; i < TreeViewLocal.Items.Count;i++)
            {
                TreeViewItem t2 = (TreeViewItem)TreeViewLocal.ItemContainerGenerator.ContainerFromItem(TreeViewLocal.Items[i]);
                t2.IsExpanded = true;
            }

But as you can see it will expends top level nodes.Any help on this highly appreciated