TreeView1_SelectedNodeChanged二次点击不能触发解决办法

protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
    {
        //点击文字后设置其下属节点是展开还是关闭
        //TreeNode node = this.TreeView1.SelectedNode;
        //node.Expanded = !node.Expanded;

        if (bool.Parse(TreeView1.SelectedNode.Expanded.ToString()))
        {
            TreeView1.SelectedNode.Collapse();
        }
        else
        {
            TreeView1.SelectedNode.Expand();
        }
        TreeView1.SelectedNode.Selected = false;
    }