基于重复的聚合日期

Question

所以我想展示一个饼图，并在 每天，为此我想总结过去 7 天的每一天。 这就是我试图做的：

IEnumerable<DateTime> commentList;
        commentList = await _context.Commentdb.Select(a => a.dateSubmit)
            .GroupBy(b => b.Day).ToListAsync();

但它不起作用，而是显示此错误：

 Cannot implicity convert type List<int,DateTime> to List<DateTime>

Answer 1

您需要在选择之前按日期和日期分组。

IEnumerable<DateTime> commentList;
    commentList = await _context.Commentdb.GroupBy(b => new { b.Day, b.dateSubmit }).Select(a => a.Key.dateSubmit)
        .ToListAsync();

更新：

 IEnumerable<DateTime> commentList;
    commentList = await _context.Commentdb.Where(x => x.dateSubmit.DayOfWeek == DayOfWeek.Sunday ||x.dateSubmit.DayOfWeek == DayOfWeek.Saturday).GroupBy(b => new { b.Day, b.dateSubmit }).Select(a => a.Key.dateSubmit)
        .ToListAsync();