添加一个节点和4个子节点
treeGXHelp.Nodes[0].Text = textBoxDropDownHelp.Text + "的主题"; treeGXHelp.Nodes[0].Nodes[0].Text = textBoxDropDownHelp.Text + "的检索内容"; treeGXHelp.Nodes[0].Nodes[1].Text = textBoxDropDownHelp.Text + "的注意事项"; treeGXHelp.Nodes[0].Nodes[2].Text = textBoxDropDownHelp.Text + "的视频"; treeGXHelp.Nodes[0].Nodes[3].Text = textBoxDropDownHelp.Text + "的经验教训";