C# Linq到Sql，用于计算和平均一组数据（无分组）

我想执行一个LINQtoSQL语句，它捕获（过滤）数据集中的计数和平均值。我所做的一切都是可行的，但它需要对数据库进行两次查询，而在一次查询中应该可以做到这一点

有趣的是，当我使用GROUPBY子句时，我可以得到一个要发出的查询

例如：

select count(*), avg(duration) from events

我的linq看起来像这样：

var x = from e in db.events
        select e;
x = from i in x
    where i.NAME == "foo"
    select i;

return new {
    count = x.Count(),
    avgDuration = x.Average(e => e.Duration)
    };

使用该代码，我得到两个查询：

SELECT AVG([t0].[DURATION]) AS [value] FROM [dbo].[EVENTS] AS [t0]

及

---

还有其他方法吗？

我能得到的最好方法是嵌套子查询：

var x = from e in db.events 
        group e by 1 into grp
        select new { 
            count = grp.Count(), 
            avgDuration = grp.Average(x => x.Duration) }

根据LINQPad，这将输出SQL：

DECLARE @p0 Int = 1

SELECT COUNT(*) AS [count], AVG([t1].[Amount]) AS [avgDuration]
FROM (
    SELECT @p0 AS [value], [t0].[Duration]
    FROM Events AS [t0]
    ) AS [t1]
GROUP BY [t1].[value]

---

从你给出的代码来看，看起来你只会得到一行两列（count，avgDuration）这是期望的结果吗？是的，这是一个表的快速快照-高查询率（对于仪表板图）哇，linq从来没有停止过让我惊讶的事情可以做什么，用来得到它的sql和用来完成任务的有趣代码+1

DECLARE @p0 Int = 1

SELECT COUNT(*) AS [count], AVG([t1].[Amount]) AS [avgDuration]
FROM (
    SELECT @p0 AS [value], [t0].[Duration]
    FROM Events AS [t0]
    ) AS [t1]
GROUP BY [t1].[value]