Question

我不确定如何使用实体框架执行此操作。我得到了以下内容：

return this.enrollments
                .Where(e => e.em_enrolled == false && e.em_result < _settings.PassMark)
                .GroupBy(e => e.em_subject_id)
                .Select(e => e.em_subject_id)
                .ToList();

我如何只检索x次出现的记录。

Answer 1

您是指具有x个或更多项目的群组吗？

return this.enrollments
                .Where(e => e.em_enrolled == false && e.em_result < _settings.PassMark)
                .GroupBy(e => e.em_subject_id)
                .Where(g => g.Count() >= x)
                .Select(g => g.Key)
                .ToList();

Answer 2

我怀疑你想要：

return this.enrollments
           .Where(e => !e.em_enrolled && e.em_result < _settings.PassMark)
           .GroupBy(e => e.em_subject_id)
           .Where(g => g.Count() >= x)
           .Select(g => g.Key)
           .ToList();

请注意，我已更改Select部分，以反映您要从组中提取组密钥的事实。（我也避免与false进行比较，将e.em_enrolled == false更改为!e.em_enrolled。当然，它们的意思相同，但我发现后者在C＃中更具惯用性。）

仅返回计数大于X的对象

2 个答案: