Select only one node in Treeview

private void treeview1_AfterCheck(object sender, TreeViewEventArgs e)
{
    if (e.Node.Checked)
    {
        DiselectParentNodes(e.Node.Parent);
        DiselectChildNodes(e.Node.Nodes);
    }
}

private void DiselectParentNodes(TreeNode parent)
{
    while (parent != null)
    {
        if (parent.Checked)
            parent.Checked = false;
        parent = parent.Parent;
    }
}

private void DiselectChildNodes(TreeNodeCollection childes)
{
    foreach (TreeNode oneChild in childes)
    {
        if (oneChild.Checked)
            oneChild.Checked = false;
        DiselectChildNodes(oneChild.Nodes);
    }
}