主题：删除基本资料行前判断是否被引用

'基础资料删除前判断是否已经被引用。条件是引用的列名必须相同。请问还能优化吗？

Dim bm1 As String = "表A"      '删除行所在表
Dim lm As String = "第一列"      '以该列为依据,判断是否被引用
Dim lm2,hhz As String
Dim bm2 As String = Tables(bm1).DataTable.name
For Each dt As DataTable In DataTables
    If DataTables(dt.Name).DataCols.Contains(lm) Then
        If Tables(bm1).current IsNot Nothing And Tables(bm1).current.isnull(lm) = False Then
            For i As Integer = Tables(bm1).BottomPosition To Tables(bm1).TopPosition Step -1
                Dim dr As Row = Tables(bm1).Rows(i)
                Dim d As String = lm & " = '" & dr(lm) & "'" 
                Dim d2 As String = "count(" & lm & ")"
                Dim d1 As String
                Dim r As Integer = eval(dt.Compute(d2,d))
                 If bm2 = dt.name Then
                    If cdec(r) > 1 Then
                        d1 = dt.Find(d & " And " & lm & " Is not null")(lm)
                        hhz = """" & dr(lm) & """" & "已经被" & """" & dt.name & """引用,禁止删除!"
                        Return hhz
                    End If
                      Else
                    If cdec(r) > 0 Then
                        d1 = dt.Find(d & " And " & lm & " Is not null")(lm)
                        hhz = """" & dr(lm) & """" & "已经被" & """" & dt.name & """引用,禁止删除!"
                        Return hhz
                    End If
                End If
            Next
        End If
    End If
Next
Dim cmd As New SQLCommand
'cmd.C 指定数据源
For Each dt As DataTable In DataTables
    bm2 = dt.name
    If bm2 IsNot Nothing And DataTables(bm2).Type <> 4 And DataTables(bm2).Type <> 5 Then
        If DataTables(bm2).DataCols.Contains(lm) Then
            If Tables(bm1).TopPosition > -1 Then
                For i As Integer = Tables(bm1).BottomPosition To Tables(bm1).TopPosition Step -1
                    Dim lz As String = Tables(bm1).Rows(i)(lm)
                    Dim nm As String = "Select Count(*) From {" & bm2 & "} Where " & lm & " = " & "'" & lz & "'"
                    cmd.CommandText = nm
                    If bm2 <> CurrentTable.DataTable.name
                        If cmd.ExecuteScalar > 0 Then
                            hhz = """" & Tables(bm1).Rows(i)(lm) & """已被""" & bm2 & """引用,禁止删除!" & vbcrlf & "如果你确认该条记录已经更改或删除,请先保存以便及时更新后台数据,再进行相应操作!"
                            Return hhz
                            Exit For
                        End If
                    Else
                            If cmd.ExecuteScalar > 1 Then
                                hhz = """" & Tables(bm1).Rows(i)(lm) & """已被""" & bm2 & """引用,禁止删除!" & vbcrlf & "如果你确认该条记录已经更改或删除,请先保存以便及时更新后台数据,再进行相应操作!"
                                Return hhz
                                Exit For
                            End If
                    End If
                Next
            End If
        End If
    End If
Next