bug，暂时变通处理一下

Dim trv As WinForm.TreeView = e.Form.Controls("TreeView1")

Dim cs As String() = "一级类别|二级类别|三级类别".split("|")
Dim os As String () = "类别编号,类别编号,类别编号".split(",")
Dim dt As DataTable = DataTables("类别")
Dim filter As String = "1=1"

For Each lvl1 As String In dt.GetValues(cs(0), filter & " and " & cs(0) & " Is not null", os(0))
    Dim nd1 = trv.nodes.add(lvl1)
    For Each lvl2 As String In dt.GetValues(cs(1), filter & " and " & cs(1) & " Is not null" & " And " & cs(0) & " = \'" & lvl1 & "\'", os(1))
        Dim nd2 = nd1.nodes.add(lvl2)
        For Each lvl3 As String In dt.GetValues(cs(2), filter & " and " & cs(2) & " Is not null" & " and " & cs(0) & " = \'" & lvl1 & "\' and " & cs(1) & " = \'" & lvl2 & "\'", os(2))
            Dim nd3 = nd2.nodes.add(lvl3)
        Next
    Next
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