Question

我有以下实体图：

Item
  IList<Prices>     
  DateTime Opened
  DateTime? Closed 

Price
  Name
  DateTime Opened
  DateTime? Closed

如何选择Closed为空的所有项目以及只有Closed为空的价格？

正如您所看到的，Item和Price具有有效期限，因此我只需选择有效的商品并使用有效价格。

我知道如何选择项目，但我不知道如何约束“嵌套”价格。

Items.Where(i => i.Closed == null).Where(i => i.Prices <need constraint prices>)

Answer 1

我想你可能正在寻找这样的东西？

Items.Where(i => !i.Closed.HasValue && i.Prices.Any(p => !p.Closed.HasValue))

这只会选择非收盘价的商品。

如果你想真正获得每个项目的非收盘价格清单，我会切换到LINQ语法并执行以下操作：

from i in Items
where !i.Closed.HasValue
from p in i.Prices
where !p.Closed.HasValue
group p by i into itemPrices
select new {
    Opened = i.Opened
    Closed = i.Closed
    Items = itemPrices
}

Answer 2

此？

    items
        .Where(x => x.Closed == null)
        .Select(x =>
            new Item
            {
                Closed = x.Closed,
                Opened = x.Opened,
                Prices = new List<Price>(x.Prices.Where(p => p.Closed == null))
            });

Answer 3

from item in items
where item.Closed == null
let prices = from price in item.Prices
             where price.Close == null
             select price
select new
{
    Item = item,
    Prices = prices.ToArray()
}

通过Linq查询使用子集合中的条件过滤父集合

3 个答案: