主题：重新登录后数据没了

下面的切工费和制造成本，重新登陆界面数据就会不见了，怎么回事？
Select Case e.DataCol.Name
    Case "商品编号", "报价等级", "QTY"
        Dim cut As DataRow = DataTables("Cutting").Find("商品编号 = '" & e.DataRow("商品编号") & "' and 等级 = '" & e.DataRow("报价等级") & "' And 从量K <= " & e.DataRow("QTY") & " And 至量K > " & e.DataRow("QTY"))
        Dim manucost As DataRow = DataTables("制造成本").Find("商品编号 = '" & e.DataRow("商品编号") & "' and 等级 = '" & e.DataRow("报价等级") & "' And 从量K <= " & e.DataRow("QTY") & " And 至量K > " & e.DataRow("QTY"))
        
        If cut IsNot Nothing Then
            e.DataRow("cutting") = cut("切工费")
        End If
        If manucost IsNot Nothing Then
            e.DataRow("制造成本") = manucost("制造成本")
        End If
END SELECT