Dim y As String = "A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z"
Dim yws As new List(of String)
For Each yw As String In y.Split("|")
yws.Add(yw)
Next
For Each dr As DataRow In DataTables("表A").DataRows
If dr.IsNull("子键")
dr("级次") = Nothing
Else
Dim s As String = yws.Indexof(dr("子键").Chars(0))
If dr("子键").Length > 1
For i As Integer = 1 To dr("子键").Length - 1
s += "." & dr("子键").Chars(i)
Next
End If
dr("级次") = s
End If
Next