Question

我有一个包含ResolvedDate和ResolvedBy列的SQL Server表。

现在我想选择这两列并计算他们的结果，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。

我希望获得已在此ResolvedDate中完成的所有活动并计算它。

我该如何实现？

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

如果您要按日期计算每件商品，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

您必须按ResolvedDate对数据进行分组，以获取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() }

要按天分组（不分小时，分钟等），您可以更改群组声明：

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() }

Answer 4

var dates = dataContext.Activities
    .Where(a => a.IsResolved && a.ResolvedBy == userId)
    .Select(a => a.ResolvedDate)
    .ToList();

var count = dates.Count;

如果您只想获得计数，您可以通过单独选择计数来加快计数：

var count = dataContext.Activities
    .Count(a => a.IsResolved && a.ResolvedBy == userId);

在LINQ中选择计数

4 个答案: