在LINQ OrderBY中排除一个值

Question

I have a list, and I would like it to be sorted by DayOfWeek, except for the case where DayOfWeek=1, which should go at the end of the list. I have tried a few variations on OrderBy and ThenBy, but it seems to continue to sort in numerical order.

I am sure this is very simple, and I don't want to change the value of the Day=1, which was the original solution

var dayOfWeeksHolder = Enumerable.Range(1, 7);   
var defaultTime = DateTime.Today.TimeOfDay;
var psList = _pickingScheduleIO.GetDayScheduleList(branchNo);
var psListByType = psList.Where(p => p.PickingSesstionTypeId == pickingSessionTypeId).ToList();

var fullList = (from d in dayOfWeeksHolder
                join s in psListByType on d equals s.DayOfWeek into grp
                from ds in grp.DefaultIfEmpty()
                // where (ds == null || ds.PickingSesstionTypeId == pickingSessionTypeId)
                select new DayScheduleVM
                {
                    PickingScheduleId = ds == null ? 0 : ds.PickingSessionScheduleId,
                    DayOfWeek = d, //d == 1 ? d + 7 : d, //in sql sunday is 1, we need to make it to 8 so it will be sorted to last
                    StartTime = ds == null ? defaultTime : ds.StartTime,
                    EndTime = ds == null ? defaultTime : ds.EndTime,
                    PickingSessionTypeId = pickingSessionTypeId
                }).OrderBy(a => a.DayOfWeek !=1).ThenBy(a => a.DayOfWeek);
return fullList.ToList();

Answer 1

You got an impression of numerical sort because of condition you used, precisely a => a.DayOfWeek != 1 . It will take all non-Sundays ( true ) and place them after Sundays ( false ), which is how OrderBy sorts boolean values.

Try either:

• .OrderByDescending(a => a.DayofWeek != 1).ThenBy(a => a.DayofWeek)
• .OrderBy(a => a.DayofWeek == 1).ThenBy(a => a.DayofWeek)

Answer 2

Try:

var fullList = (from d in dayOfWeeksHolder
                        join s in psListByType on d equals s.DayOfWeek into grp
                        from ds in grp.DefaultIfEmpty()
          //              where (ds == null || ds.PickingSesstionTypeId == pickingSessionTypeId)
                        select new DayScheduleVM
                        {
                            PickingScheduleId = ds == null ? 0 : ds.PickingSessionScheduleId,
                            DayOfWeek = d,//d == 1 ? d + 7 : d, //in sql sunday is 1, we need to make it to 8 so it will be sorted to last
                            StartTime = ds == null ? defaultTime : ds.StartTime,
                            EndTime = ds == null ? defaultTime : ds.EndTime,
                            PickingSessionTypeId = pickingSessionTypeId
                        });

return fullList.SkipWhile(a => a.DayOfWeek == 1).OrderBy(a => a.DayOfWeek).Concat(fullList.TakeWhile(a => a.DayOfWeek == 1));