VB.net按特定顺序遍历记录
VB.net按特定顺序遍历记录
提问于 2020-08-20 23:21:45
我有一个datatable，它以特定的顺序填充数据。一旦数据在表中，我需要对其他字段执行一些计算，但如果有意义的话，我需要从最下面的一行开始计算？
在那一刻，我想到了以下几点：
For Each dr As DataRow In Me.DataSet1.MyDataTable()
Dim parent_warehouse As String = dr("WH")
Dim parent_product As String = dr("ProductCode")
Dim new_material = 0
Dim new_labour = 0
Dim new_overhead = 0
Dim new_outwork = 0
Dim new_total = 0
If isassembly(parent_warehouse, parent_product) Then
If Not IsDBNull(dr("assy")) Then
For Each dr1 As DataRow In Me.DataSet1.MyDataTable()
Dim assy = dr("assy")
If assy = parent_warehouse + parent_product Then
new_material = new_material + (dr1("material") * (dr1("UsageQuantity") / dr1("Wastage")))
new_labour = new_labour + (dr1("labour") * dr1("UsageQuantity"))
new_overhead = new_overhead + (dr1("overhead") * dr1("UsageQuantity"))
new_outwork = new_outwork + (dr1("outwork") * dr1("UsageQuantity"))
new_total = new_material + new_labour + new_overhead + new_outwork
End If
Next
dr("new_material") = new_material
dr("new_labour") = new_labour
dr("new_overhead") = new_overhead
dr("new_outwork") = new_outwork
dr("new_total") = new_total
Else
GoTo skip
End If
Else
dr("new_material") = dr("material")
dr("new_labour") = dr("labour")
dr("new_overhead") = dr("overhead")
dr("new_outwork") = dr("outwork")
dr("new_total") = dr("total")
End If
skip:
Next我目前遇到的问题是，当它循环遍历记录时，它会从上到下循环，我希望它从下到上循环，因为成本应该是从底部产品向上累积的，这样它们的父产品就会获得新的成本，并一直向上循环到顶部产品。
回答 2
Stack Overflow用户
回答已采纳
发布于 2020-08-21 18:52:36
反向循环将是您的最佳选择。您将使用带有Step -1的For循环
' declare a variable for our DataTable
Dim dt As DataTable = Me.DataSet1.MyDataTable()
' we're setting our 'i' variable to the last row (account for 0-index)
' in a typical For Loop, the Step is +1, but we're specifying -1 to go backwards
For i as Integer = dt.Rows.Count - 1 to 0 Step -1
' execute logic
' something like CDec(dt.Rows(i).Item("DecimalColumn")) to convert decimal type
' CInt(), CStr(), CDate() are also very useful, Integer, String, and Date respectively
NextStack Overflow用户
发布于 2020-08-20 23:30:52
我认为您需要对表的默认视图进行排序，然后遍历默认视图。
Me.DataSet1.MyDataTable.defaultview.sort = "material", "labor" 'etc.
For Each dr As DataRowView In Me.DataSet1.MyDataTable.defaultview
'...*根据@jmcilhinney在评论中的更正进行了编辑。--谢谢！
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/63508274
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