Question

我正在尝试在C＃表达式中编写LINQ查询，以获取采购订单的概述，其中包含一个表TblPODetails以及采购订单中的项目列表。我想获取此表中的每个订单项，然后将已收到的项目总数添加到表TblPOReceipts中。如果没有收到任何项目，则TblPOReceipts显示为null，查询返回0结果。

如何在TblPOReceipts中允许空值并仍然可以从TblPODetails获取其余结果？

这是我的疑问：

from podetail in TblPODetails
from pricebook in TblPriceBooks.Where(x => x.ItemID == podetail.ItemID).DefaultIfEmpty()
from receipt in TblPOReceipts.Where(x => x.ItemID ==podetail.ItemID).DefaultIfEmpty()

where podetail.PONumber == 4707
where receipt.PONumber == 4707

group new { receipt, podetail, pricebook } by new {pricebook, podetail, receipt.QuantityReceived } into g

select new {
    g.Key.podetail.ItemDescription,
    TotalReceived = g.Sum (x => x.receipt.QuantityReceived),
    QuantityPosted = g.Where (x => x.receipt.Posted == true).Sum (x => x.receipt.QuantityReceived),
    g.Key.podetail.ItemID,
    g.Key.podetail.QuantityOrdered,
    g.Key.podetail.ProjectedCost,
    g.Key.podetail.TotalProjectedCost,
    g.Key.pricebook.BaseCost,
    g.Key.pricebook.ItemURL
}

Answer 1

在我使用的查询中，这是一个愚蠢的错误：

where receipt.PONumber == 4707

为null，因此没有返回任何结果。

我已经解决了这个问题：

where receipt.PONumber == null || receipt.PONumber == 4707

我也把这个总和作为一个int。

    TotalReceived = (int?)g.Sum (x => x.receipt.QuantityReceived),
    QuantityPosted = (int?)g.Where (x => x.receipt.Posted == true).Sum (x => x.receipt.QuantityReceived),

允许在组中使用空表

1 个答案: