C# 如何使用LINQ从列表中的列表中获取分组值
我希望使用LINQ检索一个列表中属性值总和的列表,该列表本身是另一个列表的属性,按父列表中的属性分组 为了解释,我有一份市场报价清单,上面有一系列产品的交易日期和交易时间,以及每个报价中的价格和数量区间清单。我的课程是:C# 如何使用LINQ从列表中的列表中获取分组值,c#,list,linq,C#,List,Linq,我希望使用LINQ检索一个列表中属性值总和的列表,该列表本身是另一个列表的属性,按父列表中的属性分组 为了解释,我有一份市场报价清单,上面有一系列产品的交易日期和交易时间,以及每个报价中的价格和数量区间清单。我的课程是: public class Offer { public DateTime TradingDate { get; set; } public int HourOfDay { get; set; } public string ProductName { g
public class Offer
{
public DateTime TradingDate { get; set; }
public int HourOfDay { get; set; }
public string ProductName { get; set; }
public List<Band> OfferBands { get; set; }
}
public class Band
{
public decimal Price { get; set; }
public double Quantity { get; set; }
}
但是我不知道如何通过GroupBy
TradingDate和HourOfDay
检索数量的总和。对于不同的产品,可以有多个报盘
s和多个报盘
s,以及各种组合的报盘
价格s,我只想得到按日期和时间分组的特定价格下所有产品的数量之和
我可以通过编程实现这一点,但我想要一个LINQ解决方案。谢谢你的帮助
编辑:
我忘了提到的是,如果交易日期和小时数在指定的价格下没有数量
,我想检索double.NaN
(或0
)
示例数据列表提供
包含六个提供
s:
TradingDate | HourOfDay | ProductName | OfferBands
===================================================================
01/01/2017 | 1 | Chocolate | Price = 2, Quantity = 6
| | | Price = 5, Quantity = 10
-------------------------------------------------------------------
01/01/2017 | 2 | Chocolate | Price = 3, Quantity = 6
| | | Price = 5, Quantity = 20
-------------------------------------------------------------------
02/01/2017 | 1 | Chocolate | Price = 3, Quantity = 7
| | | Price = 6, Quantity = 9
-------------------------------------------------------------------
01/01/2017 | 1 | Cake | Price = 5, Quantity = 11
| | | Price = 8, Quantity = 3
-------------------------------------------------------------------
01/01/2017 | 2 | Cake | Price = 2, Quantity = 1
| | | Price = 8, Quantity = 4
-------------------------------------------------------------------
02/01/2017 | 1 | Cake | Price = 3, Quantity = 9
| | | Price = 5, Quantity = 13
-------------------------------------------------------------------
选择给定价格的数量总和,按日期和时间分组,将给出列表
输出:
其中价格>=5
{ 24, 24, 22 }
其中价格=2
{ 6, 1, double.NaN }
其中价格=3
{ double.NaN, 6, 16 }
…其中,输出是2017年1月1日第1小时、2017年1月1日第2小时和2017年1月2日第1小时的所有产品在规定价格下的数量总和
希望这一点很清楚。我相信我已经能够管理您想要的分组,尽管我还没有对(数量)*(无论价格是否符合某些条件)进行求和,因为希望这是您可以定制的东西,但您需要
为了将事情分组,我必须使用几个嵌套的投影,并单独进行每个分组(解决这个问题实际上很有趣,最大的症结在于LINQ的iGroup并不像您预期的那样简单,所以每次分组时,我都使用Select进行投影):
希望,这将给你足够的时间开始做你的总和,无论你需要什么额外的检查0项,价格不够高,等等
请注意,如果您直接使用数据库,此查询可能不是最有效的—它可能会提取比此时实际需要的更多的信息。不过,我对您正在进行的工作了解不够,无法开始对其进行优化。var offers=new List();
var offers = new List<Offer>();
// flatten the nested list linq-style
var flat = from x in offers
from y in x.OfferBands
select new {x.TradingDate, x.HourOfDay, x.ProductName, y.Price, y.Quantity};
var grouped = from x in flat
group x by new {x.TradingDate, x.HourOfDay, x.ProductName}
into g
select new
{
g.Key.TradingDate,
g.Key.HourOfDay,
g.Key.ProductName,
OfferBands = (from y in g
group y by new {y.Price}
into q
select new {Price = q.Key, Quantity = q.Sum(_ => _.Quantity)}).ToList()
};
foreach (var item in grouped)
{
Console.WriteLine(
"TradingDate = {0}, HourOfDay = {1}, ProductName = {2}",
item.TradingDate,
item.HourOfDay,
item.ProductName);
foreach (var offer in item.OfferBands)
Console.WriteLine(" Price = {0}, Qty = {1}", offer.Price, offer.Quantity);
}
//展平嵌套列表linq样式
var flat=从x开始,在报价中
从y到x
选择新{x.TradingDate,x.HourOfDay,x.ProductName,y.Price,y.Quantity};
var分组=从平面中的x开始
按新{x.TradingDate,x.HourOfDay,x.ProductName}划分的x组
进入g
选择新的
{
g、 Key.TradingDate,
g、 基恩·霍洛夫日,
g、 Key.ProductName,
OfferBands=(从y到g)
按新{y.Price}划分的y组
进入q
选择新的{Price=q.Key,Quantity=q.Sum({u=>{uq.Quantity)})
};
foreach(分组中的var项目)
{
控制台写入线(
“TradingDate={0},HourOfDay={1},ProductName={2}”,
item.TradingDate,
项目1.1天,
项目名称);
foreach(项目中的var报价。报价单)
WriteLine(“Price={0},Qty={1}”,offer.Price,offer.Quantity);
}
首先,您需要过滤以获得所需的报价
s和匹配的报价
您可以创建/传入一个过滤器,如果您想使其成为一个函数,我将以内联方式定义它:
Func<Band, bool> filter = (Band b) => b.Price == 3;
现在,由于您希望为原始数据中已过滤掉的TradingDate
+HourOfDay
包含空槽,请将过滤后的数据分组并创建字典:
var mapQuantity = filteredOffers.GroupBy(o => new { o.TradingDate, o.HourOfDay })
.Select(og => new { og.Key.TradingDate, og.Key.HourOfDay, QuantitySum = og.Sum(o => o.OfferBands.Sum(ob => ob.Quantity)) })
.ToDictionary(og => new { og.TradingDate, og.HourOfDay }, og => og.QuantitySum);
然后,返回原始的报价
组,找到所有不同的时段(TradingDate
+HourOfDday
),并将它们与QuantitySum
匹配,用double.NaN
填充空时段,并转换为列表
:
var ans = offers.Select(o => new { o.TradingDate, o.HourOfDay }).Distinct().OrderBy(g => g.TradingDate).ThenBy(g => g.HourOfDay).Select(g => mapQuantity.TryGetValue(g, out var sumq) ? sumq : double.NaN).ToList();
经过重新思考,我意识到可以通过保留过滤器过滤器中的空插槽来简化,然后在分组后设置其值:
var filteredOffers = offers.Select(o => new { TradingDate = o.TradingDate, HourOfDay = o.HourOfDay, OfferBands = o.OfferBands.Where(filter).ToList() });
var ans = filteredOffers.GroupBy(o => new { o.TradingDate, o.HourOfDay })
.OrderBy(og => og.Key.TradingDate).ThenBy(og => og.Key.HourOfDay)
.Select(og => (og.Sum(o => o.OfferBands.Count) > 0 ? og.Sum(o => o.OfferBands.Sum(ob => ob.Quantity)) : double.NaN));
通过使用i分组
键
记住插槽,您可以简化查询:
var ans = offers.GroupBy(o => new { o.TradingDate, o.HourOfDay }, o => o.OfferBands)
.OrderBy(obg => obg.Key.TradingDate).ThenBy(obg => obg.Key.HourOfDay)
.Select(obg => {
var filteredOBs = obg.SelectMany(ob => ob).Where(filter).ToList();
return filteredOBs.Count > 0 ? filteredOBs.Sum(b => b.Quantity) : double.NaN;
});
如果您愿意放弃double.NaN
而改为零,您可以让这更简单:
var ans = offers.GroupBy(o => new { o.TradingDate, o.HourOfDay }, o => o.OfferBands)
.OrderBy(obg => obg.Key.TradingDate).ThenBy(obg => obg.Key.HourOfDay)
.Select(obg => obg.SelectMany(ob => ob).Where(filter).Sum(b => b.Quantity));
最后,为了完成这项任务,一些特殊的扩展方法可以保留NaN
返回属性,并使用简单的查询表单:
public static class Ext {
static double ValuePreservingAdd(double a, double b) => double.IsNaN(a) ? b : double.IsNaN(b) ? a : a + b;
public static double ValuePreservingSum(this IEnumerable<double> src) => src.Aggregate(double.NaN, (a, b) => ValuePreservingAdd(a, b));
public static double ValuePreservingSum<T>(this IEnumerable<T> src, Func<T, double> select) => src.Select(s => select(s)).Aggregate(double.NaN, (a, b) => ValuePreservingAdd(a, b));
}
var ans = offers.GroupBy(o => new { o.TradingDate, o.HourOfDay }, o => o.OfferBands)
.OrderBy(obg => obg.Key.TradingDate).ThenBy(obg => obg.Key.HourOfDay)
.Select(obg => obg.SelectMany(ob => ob).Where(filter).ValuePreservingSum(b => b.Quantity));
公共静态类Ext{
静态双值保存ADD(双a,双b)=>double.IsNaN(a)→b:double.IsNaN(b)→a:a+b;
公共静态双值保存sum(此IEnumerable src)=>src.聚合(double.NaN,(a,b)=>ValuePreservingAdd(a,b));
public static double ValuePreservingSum(此IEnumerable src,Func select)=>src.select(s=>select(s)).Aggregate(double.NaN,(a,b)=>ValuePreservingAdd(a,b));
}
var ans=offers.GroupBy(o=>new{o.TradingDate,o.HourOfDay},o=>o.OfferBands)
.OrderBy(obg=>obg.Key.TradingDate)。然后by(obg=>obg.Key.HourOfDay)
.Select(obg=>obg.SelectMany(ob=>ob).Where(filter.ValuePreservingSum(b=>b.Quantity));
出于好奇,HourOfDay
是否与TradingDate.Hour
不同?如果不是,为什么要将小时存储在多个地方?看来我
var ans = offers.GroupBy(o => new { o.TradingDate, o.HourOfDay }, o => o.OfferBands)
.OrderBy(obg => obg.Key.TradingDate).ThenBy(obg => obg.Key.HourOfDay)
.Select(obg => {
var filteredOBs = obg.SelectMany(ob => ob).Where(filter).ToList();
return filteredOBs.Count > 0 ? filteredOBs.Sum(b => b.Quantity) : double.NaN;
});
var ans = offers.GroupBy(o => new { o.TradingDate, o.HourOfDay }, o => o.OfferBands)
.OrderBy(obg => obg.Key.TradingDate).ThenBy(obg => obg.Key.HourOfDay)
.Select(obg => obg.SelectMany(ob => ob).Where(filter).Sum(b => b.Quantity));
public static class Ext {
static double ValuePreservingAdd(double a, double b) => double.IsNaN(a) ? b : double.IsNaN(b) ? a : a + b;
public static double ValuePreservingSum(this IEnumerable<double> src) => src.Aggregate(double.NaN, (a, b) => ValuePreservingAdd(a, b));
public static double ValuePreservingSum<T>(this IEnumerable<T> src, Func<T, double> select) => src.Select(s => select(s)).Aggregate(double.NaN, (a, b) => ValuePreservingAdd(a, b));
}
var ans = offers.GroupBy(o => new { o.TradingDate, o.HourOfDay }, o => o.OfferBands)
.OrderBy(obg => obg.Key.TradingDate).ThenBy(obg => obg.Key.HourOfDay)
.Select(obg => obg.SelectMany(ob => ob).Where(filter).ValuePreservingSum(b => b.Quantity));