主题：请教计算剩余天数

请教计算剩余天数，下面代码提示错误，请老师指导一下

Select Case e.DataCol.Name

    Case "到期日期"

        Dim dr As DataRow = e.DataRow

        Dim d As Date = Date.Today

        If dr.IsNull("到期日期") Then

            dr("剩余天数") = Nothing

        Else

            Dim tp As TimeSpan = dr("到期日期") - d

            dr("剩余天数") = tp.TotalDays

        End If

End Select

谢谢蓝老师！