C# Linq 选择分组依据
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Linq Select Group By
提问by Lucifer
I have the following class structure :
我有以下类结构：
public class PriceLog
{
public DateTime LogDateTime {get; set;}
public int Price {get; set;}
}
For a List< PriceLog >I want a Linq query to generate an output which is equivalent to the data represented as below:
对于List< PriceLog >我想要一个 Linq 查询来生成一个输出，它相当于如下表示的数据：
LogDateTime | AVG(Price)
Jan 2012 | 2000
Feb 2012 | 3000
日志日期时间 |
2012 年 1 月的AVG(价格) | 2000
2012年2 月 | 3000
Simply : I want to compute the average price over each month of the year.
Note: LogDateTime property should be formatted as LogDateTime.ToString("MMM yyyy")
简单地说：我想计算一年中每个月的平均价格。
注意：LogDateTime 属性的格式应为LogDateTime.ToString("MMM yyyy")
I have tried the following, but not sure whether it will generate the desired result:
我尝试了以下方法，但不确定它是否会产生所需的结果：
var result = from priceLog in PriceLogList
group priceLog by priceLog.LogDateTime.ToString("MMM yyyy") into dateGroup
select new PriceLog { GoldPrice = (int)dateGroup.Average(p => p.GoldPrice), SilverPrice = (int)dateGroup.Average(p => p.SilverPrice)};
采纳答案by Sergey Berezovskiy
This will give you sequence of anonymous objects, containing date string and two properties with average price:
这将为您提供匿名对象序列，包含日期字符串和两个具有平均价格的属性：
var query = from p in PriceLogList
group p by p.LogDateTime.ToString("MMM yyyy") into g
select new {
LogDate = g.Key,
AvgGoldPrice = (int)g.Average(x => x.GoldPrice),
AvgSilverPrice = (int)g.Average(x => x.SilverPrice)
};
If you need to get list of PriceLog objects:
如果您需要获取 PriceLog 对象列表：
var query = from p in PriceLogList
group p by p.LogDateTime.ToString("MMM yyyy") into g
select new PriceLog {
LogDateTime = DateTime.Parse(g.Key),
GoldPrice = (int)g.Average(x => x.GoldPrice),
SilverPrice = (int)g.Average(x => x.SilverPrice)
};
回答by MuhammadHani
from p in PriceLog
group p by p.LogDateTime.ToString("MMM") into g
select new
{
LogDate = g.Key.ToString("MMM yyyy"),
GoldPrice = (int)dateGroup.Average(p => p.GoldPrice),
SilverPrice = (int)dateGroup.Average(p => p.SilverPrice)
}
回答by amartine
You should try it like this:
你应该像这样尝试：
var result =
from priceLog in PriceLogList
group priceLog by priceLog.LogDateTime.ToString("MMM yyyy") into dateGroup
select new {
LogDateTime = dateGroup.Key,
AvgPrice = dateGroup.Average(priceLog => priceLog.Price)
};
回答by yo chauhan
var result = priceLog.GroupBy(s => s.LogDateTime.ToString("MMM yyyy")).Select(grp => new PriceLog() { LogDateTime = Convert.ToDateTime(grp.Key), Price = (int)grp.Average(p => p.Price) }).ToList();
I have converted it to int because my Price field was int and Average method return double .I hope this will help
我已将它转换为 int 因为我的 Price 字段是 int 并且 Average 方法返回 double 。我希望这会有所帮助
