vb.net treeview

' 创建一个新的 TreeView 控件实例
Dim treeView As New TreeView()
treeView.Location = New Point(10, 10)
treeView.Size = New Size(200, 300)

' 添加根节点
Dim rootNode As TreeNode = treeView.Nodes.Add("Root Node")

' 添加子节点
Dim childNode1 As TreeNode = rootNode.Nodes.Add("Child Node 1")
Dim childNode2 As TreeNode = rootNode.Nodes.Add("Child Node 2")

' 添加孙节点
childNode1.Nodes.Add("Grandchild Node 1")
childNode1.Nodes.Add("Grandchild Node 2")

' 将 TreeView 控件添加到窗体中
Me.Controls.Add(treeView)

Private Sub TreeView1_BeforeExpand(sender As Object, e As TreeViewCancelEventArgs) Handles TreeView1.BeforeExpand
    If e.Node.Nodes.Count = 1 AndAlso e.Node.Nodes(0).Text = "Loading..." Then
        ' 模拟异步加载数据
        Dim loadedNodes As List(Of TreeNode) = LoadNodesFromDatabase(e.Node.Tag)
        e.Node.Nodes.Clear()
        For Each node As TreeNode In loadedNodes
            e.Node.Nodes.Add(node)
        Next
    End If
End Sub

Private Function LoadNodesFromDatabase(parentId As Integer) As List(Of TreeNode)
    ' 这里应该是从数据库或其他数据源加载数据的逻辑
    ' 返回一个 TreeNode 列表
End Function