主题：[求助]这语句怎么编？

Select Case e.DataCol.Name 

    Case "第四列","第五列","第六列","第七列"

        Dim Filter As String = "[编码] = '" & e.DataRow("编码") & "'"

        Dim drs As List(Of DataRow) = DataTables("表A").Select(Filter)

        For Each dr As DataRow In drs

     If   IsNull(e.NewValue) Then   　　　　　这句不会编写。（如果为空是就不替换）

          dr(e.DataCol.Name) = e.NewValue

       End If

  Next 

 End Select