Question

I am trying to convert this SQL to linq syntax, but I m having some difficulties at that.

SELECT trans_date, count(*) FROM table1
GROUP BY trans_date

Result
01-01-2001 | 12
03-01-2001 | 45

var q = from a in table1
let dt = q.trans_date.value
group q by new {y = dt.Year.ToString(), m = dt.Month.ToString(), d = dt.Day.toString()}
into g
select new { int NumOf = g.Count(), DateTime TransDate = DateTime.Parse(g.Key.y + g.key.m + g.Key.d)}

最后一次“改写”的日期。 Parse给我留下了一个错误。

如何处理这一术语——日期是不可否认的日期和取得我的成果?

Answer 1

一次,您不再收到runtime。与这部法典的错误——你被带上compile-time,因为你的代码是有效的C#。

为此:

var q = from a in table1
        group a by a.trans_date.value.Date into g
        select new {
            Count = g.Count(),
            TransDate = g.Key
        };

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