Select e.DataCol.Name
    Case "MLMC","MLLB"
        If e.DataRow.IsNull("MLMC") OrElse e.DataRow.IsNull("MLLB") Then
            e.DataRow("MLBH") = Nothing
        Else
            Dim bfry As String = e.DataRow("MLLB")
            If e.DataRow("MLLB") = "MM1" Then
                bfry = "SZ"
            ElseIf e.DataRow("MLLB") = "MM2" Then
                bfry = "ZZ"
            ElseIf e.DataRow("MLLB") = "MM3" Then
                bfry = "HB"
            ElseIf e.DataRow("MLLB") = "MM4" Then
                bfry = "WF"
            End If
    
            Dim bflx As String = GetPy(e.DataRow("MLMC").substring(0,2) ,True)
                      
            Dim bf As String = "ML"
            Dim d As Date = Date.Today()
            Dim bh As String = bf & Format(d,"yy") & bflx &Format(d,"MM") & bfry & Format(d,"yy") & "-"
           
            Dim max As String
            Dim idx As Integer
            max = e.DataTable.Compute("Max(MLBH)","MLBH like \'" & bh & "%\'")
            If len(max) = 14 Then   \'如果存在最大编号
                idx = CInt(max.Substring(bh.Length)) + 1 \'获得最大编号的后三位顺序号,并加1
            Else
                idx = 1 \'否则顺序号等于1
            End If
            e.DataRow("MLBH") = bh & Format(idx,"000")
        End If
End Select

能帮我看一下吗？不能按序编号，不知道是怎么回事。

知道怎么回事了， If len(max) = 14 Then   \'如果存在最大编号
应该是 If max = “” Then