主题：BOM嵌套检查的内部函数死循环。

其实很简单，不需要递归，你在命令窗口执行：

Dim drs As New List(of DataRow)
Dim keys As New List(of String)
For Each dr As DataRow In DataTables("表A").DataRows
    keys.Clear
    Dim dr1 As DataRow = dr
    keys.Add(dr("键"))
    Do
        Dim pkey As String = dr1("父键")
        If keys.Contains(pkey)
            drs.Add(dr)
            Exit Do
        Else
            keys.Add(pkey)
            dr1 = DataTables("表A").Find("键 = '" &  pkey  & "'")
            If dr1 Is Nothing Then
                Exit Do
            End If
        End If
    Loop
Next

'列出死循环的行的标题
For Each dr As DataRow In drs
    output.show(dr("标题"))
Next