如何设置使在treeview中点击父节点，父节点下所有的子节点不可，点击子节点，该节点不可选。

protected void tree1_SelectedNodeChanged(object sender, TreeNodeEventArgs e)
{
TreeView tree= sender as TreeView ;
if(tree != null && tree.SelectedNode != null)
{
TreeNode parent = tree.SelectedNode;
foreach(TreeNode son in parent.ChildNodes)
{
//通过TreeNodeSelectAction控制节点状态
son..SelectAction=TreeNodeSelectAction.None;
}
}
}