I have a timetable list. I want to pull two data by grouping over this list. However, I was not successful. My data.

My code

_contex.timetable.where(i=>i.yid==6).DistinctBy(i => i.xid).Select(i => new { i.xid, i.gid, i.date}).ToListAsync();

but null value or error. What i want to do.

I want to get the last data of the date and also the gid fields.

Sorry for my bad English, I hope I explained.

CodePudding user response：

You group them up by xid and pick the latest date row from each group.

var result = context.timetable
                .GroupBy(t => t.xid)
                .Select(g => g.OrderByDescending(r => r.date).First())
                .ToListAsync();

CodePudding user response：

From your question, I think you want to get the data of Id,date,gid from latest date row which group by xid, So you can try to refer this code:

var result = await _context.timetables.GroupBy(x => x.xid)
              .Select(y => y.OrderByDescending(r => r.date)
               .Select(a=> new {a.Id,a.date,a.gid}).FirstOrDefault())
                .ToListAsync();