asp.net treeview单击父类文本展开子类如何实现

'只展开不收缩(现在网络不通了,有什么事下载个百度hi聊聊,不知道对你有没有帮助)
Private Root As System.Web.UI.WebControls.TreeNode

Private SelectNode As TreeNode

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

If Not Page.IsPostBack Then

'//添加根节点
Root = New TreeNode("根节点", "root")
Me.TreeView1.Nodes.Add(Root)

'//添加一级节点

Dim FirstNode As New TreeNode("一级节点", "First")
Me.TreeView1.FindNode("root").ChildNodes.Add(FirstNode)

'//添加一级节点

Dim SecondNode As New TreeNode("二级节点", "Second")
Me.TreeView1.Nodes(0).ChildNodes(0).ChildNodes.Add(SecondNode)

Me.TreeView1.ShowExpandCollapse = False

Me.TreeView1.CollapseAll()