You have to convert them to System.Windows.Controls.TreeViewItem
first.
public TreeWindow(TreeNode node)
{
InitializeComponent();
treeView.Items.Add(ConvertToWpf(node));
}
TreeViewItem ConvertToWpf(TreeNode node)
{
var wpfItem = new TreeViewItem();
wpfItem.Header = node.Text;
foreach(var child in node.Nodes)
{
wpfItem.Items.Add(ConvertToWpf(child));
}
return wpfItem;
}