C# LINQ 查询 - 分组依据
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/499578/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
C# LINQ Query - Group By
提问by
I'm having a hard time understanding how I can form a LINQ query to do the following:
我很难理解如何形成一个 LINQ 查询来执行以下操作：
I have a table CallLogs and I want to get back a single result which represents the call that has the longest duration.
我有一个 CallLogs 表，我想取回一个代表持续时间最长的呼叫的结果。
The row looks like this:
该行如下所示：
[ID] [RemoteParty] [Duration]
[ID] [RemoteParty] [持续时间]
There can be multiple rows for the same RemoteParty, each which represents a call of a particular duration. I'm wanting to know which RemoteParty has the longest total duration.
同一个 RemoteParty 可以有多行，每行代表一个特定持续时间的调用。我想知道哪个 RemoteParty 的总持续时间最长。
Using LINQ, I got this far:
使用 LINQ，我做到了这一点：
var callStats = (from c in database.CallLogs
group c by c.RemoteParty into d
select new
{
RemoteParty = d.Key,
TotalDuration = d.Sum(x => x.Duration)
});
So now I have a grouped result with the total duration for each RemoteParty but I need the maximum single result.
所以现在我有一个带有每个 RemoteParty 总持续时间的分组结果，但我需要最大的单个结果。
[DistinctRemoteParty1] [Duration]
[DistinctRemoteParty2] [Duration]
[DistinctRemotePartyN] [Duration]
[DistinctRemoteParty1] [持续时间]
[DistinctRemoteParty2] [持续时间]
[DistinctRemotePartyN] [持续时间]
How can I modify the query to achieve this?
如何修改查询以实现此目的？
回答by tvanfosson
Order the result and return the first one.
对结果进行排序并返回第一个。
var callStats = (from c in database.CallLogs
group c by c.RemoteParty into d
select new
{
RemoteParty = d.Key,
TotalDuration = d.Sum(x => x.Duration)
});
callStats = callStats.OrderByDescending( a => a.TotalDuration )
.FirstOrDefault();
回答by flq
Have a look at the "Max" extension method from linq
看看 linq 的“Max”扩展方法
callStats.Max(g=>g.TotalDuration);
