主题：增加子节点父键要保持和已有分组不变

Dim tr As WinForm.TreeView = e.Form.Controls("TreeView1")
Dim sd As WinForm.TreeNode=tr.SelectedNode '当前选择的项
Dim dt As DataTable=DataTables(vars("editTable"))

If sd Is Nothing Then Return
Dim name As String
Dim typ As String
If sd.Level = 1 Then
    MessageBox.Show("不能再增加子节点了!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
Else
    Dim r As DataRow=dt.AddNew
    If sd.Level = 0 Then

        r("分组")=sd.Text
        r("名称")="新节点"
        r("父键")=dt.Compute("Max(父键)","父键 ='" & sd.name & "'")
    End If
    sd = sd.Nodes.Add("新节点")
    tr.SelectedNode = sd
    tr.Select
    tr.BeginEdit()
End If