主题：五级目录树的建立

5、“增加子节点”按钮的Click事件代码：

Dim tr As WinForm.TreeView
Dim nd As WinForm.TreeNode
tr = e.Form.Controls("TreeView1")
nd = tr.SelectedNode
If nd IsNot Nothing Then
    If nd.Level = 2 Then
        MessageBox.Show("最多允许三层节点!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
    Else
        Dim dr As DataRow = DataTables("表A").AddNew
        If nd.Level = 0 Then
            dr("大类") = nd.Text
            dr("二类") = "新节点"
        ElseIf nd.Level = 1
            dr("大类") = nd.ParentNode.Text
            dr("二类") = nd.text
            dr("三类") = "新节点"
        End If
        nd = nd.Nodes.Add("新节点")
        tr.SelectedNode = nd
        tr.Select()
        tr.BeginEdit()
    End If
End If

6、“删除”按钮的Click事件代码：

Dim tr As WinForm.TreeView = e.Form.Controls("TreeView1")
Dim nd As WinForm.TreeNode = tr.SelectedNode
If nd IsNot Nothing Then
    Dim pth() As String = nd.FullPath.Split("\")
    Select Case nd.Level
    Case 0
        DataTables("表A").DeleteFor("大类 = '" & pth(0) & "'")
    Case 1
        DataTables("表A").DeleteFor("大类 = '" & pth(0) & "' And 二类 = '" & pth(1) & "'")
    Case 2
        DataTables("表A").DeleteFor("大类 = '" & pth(0) & "' And 二类 = '" & pth(1) & "' And 三类 = '" & pth(2) & "'")
    End Select
    nd.Delete()
End If
tr.Select()

7、目录树AfterEditNode事件代码：