主题：[求助]如此求和？

Dim sum As Double = 0
For Each ls As String In DataTables("送货明细表").GetValues("流水号", "送货单号 = '" & e.Value & "'")
    Dim fdr As DataRow = DataTables("送货明细表").find("sum(基膜净重)", "送货单号 = '" & e.value & "' and 流水号 = '" & ls & "'")
    If fdr IsNot Nothing Then
        sum += fdr("基膜重量")
    End If
Next
forms("打印送货单").Controls("基膜重量").text = sum