Button 對 TreeView1 所有節點的全選

protected void Button1_Click(object sender, EventArgs e)
    {
        for (int i = 0; i < this.TreeView1.Nodes.Count; i++)//迴圈根節點
        {
            if (TreeView1.Nodes[i].Checked == false)//判斷是否被選中
            {
                TreeView1.Nodes[i].Checked = true;
                for (int j = 0; j < this.TreeView1.Nodes[i].ChildNodes.Count; j++)//迴圈當前節點的第一級子節點
                {
                    if (this.TreeView1.Nodes[i].ChildNodes[j].Checked == false)
                    {
                        TreeView1.Nodes[i].ChildNodes[j].Checked = true;
                    }
                }
            }
        }
    }