C＃LINQ查询 - 分组依据 [英] C# LINQ Query - Group By

问题描述

我有一个很难理解我怎么能形成一个LINQ查询执行以下操作：

I'm having a hard time understanding how I can form a LINQ query to do the following:

我有一个表CallLogs，我想回到从而重新$ P $一个结果psents具有持续时间最长的呼叫。

I have a table CallLogs and I want to get back a single result which represents the call that has the longest duration.

该行看起来是这样的：

[ID] [RemoteParty] [时间]

[ID] [RemoteParty] [Duration]

可以有多个行为同一Re​​moteParty，其中每一个重新presents一个特定持续时间的呼叫。我想知道哪些RemoteParty具有最长的总时间。

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.

使用LINQ，我走到这一步：

Using LINQ, I got this far:

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)
                 });

所以，现在我有一个分组结果，总的持续时间为每个RemoteParty但我需要的最大单一结果。

So now I have a grouped result with the total duration for each RemoteParty but I need the maximum single result.

[DistinctRemoteParty1] [时间]

[DistinctRemoteParty1] [Duration]

[DistinctRemoteParty2] [时间]

[DistinctRemoteParty2] [Duration]

[DistinctRemotePartyN] [时间]

[DistinctRemotePartyN] [Duration]

我怎样才能修改查询实现这一目标？

How can I modify the query to achieve this?

推荐答案

订单的结果，返回的第一个。

Order the result and return the first one.

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();

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