private void button1_Click(object sender, EventArgs e)
        {
            //禁用第一个节点
            treeView1.Nodes[0].ForeColor = SystemColors.Control;        
 }

        private void treeView1_BeforeSelect(object sender, TreeViewCancelEventArgs e)
        {
            if (e.Node != null)
            {
                if (e.Node.ForeColor == SystemColors.Control)
                {
                    e.Cancel = true;  //不让选中禁用节点
                }
            }
        }

        private void treeView1_BeforeCheck(object sender, TreeViewCancelEventArgs e)
        {
            if (e.Node != null)
            {
                if (e.Node.ForeColor == SystemColors.Control)
                {
                    e.Cancel = true; //不让选中禁用节点

                }
            }
        }