在LINQ中选择计数

Question

我有一个带有列ResolvedDate和的SQL Server表ResolvedBy.

现在我想选择这两列并计算它们的结果,我认为我会这样实现:

_dataContext.Activities
    .Where(a => a.IsResolved && a.ResolvedBy == userId)
    .Select(a => new { a.ResolvedDate, ***COUNT*** });

如您所见,Count-Part缺失.

我希望得到所有已在此ResolvedDate中完成的活动并计算它.

我该如何实现呢？

Answer 1

from a in dataContext.Activities
where a.IsResolved && a.ResolvedBy == userId
group a by a.ResolvedDate into g
select new {ResolvedOn=g.Key, NumberResolved= g.Count()}

Answer 2

如果您尝试按日期计算每个项目,则需要使用GroupBy:

var countsByDate = _dateContext.Activities
                           .Where(a => a.IsResolved && a.ResolvedBy == userId)
                           .GroupBy(a => a.ResolvedDate)
                           .Select(g => new {ResolvedDate = g.Key, Count = g.Count() });

Answer 3

您必须通过ResolvedDate对数据进行分组,以获得每天解决的活动数量.

var dates = from a in dataContext.Activities
            where a.IsResolved && a.ResolvedBy == userId
            group a by a.ResolvedDate into g
            select new { Date = g.Key, Count = g.Count() }

要按日分组(不分小时,分钟等),您可以更改组语句:

var dates = from a in dataContext.Activities
            where a.IsResolved && a.ResolvedBy == userId
            group a by a.ResolvedDate.Date into g
            select new { Date = g.Key, Count = g.Count() }