Check all nodes parent in treeview c#

thank you. i have done it.

^^ thank you :).
i tried:
private void treeView1_AfterCheck(object sender, TreeViewEventArgs e)
{
if (e.Node.Checked)
{
if (e.Node.Text == "check all")
{
if (treeView1.Nodes.Count > 0)
{
for (int i = 0; i < treeView1.Nodes.Count - 1; i++)
{
treeView1.Nodes[i].Checked = true;
foreach (TreeNode child in treeView1.Nodes[i].Nodes)
{
child.Checked = true;
}
}
}
}
}
}