Question

I have a linq which groups prices by month works perfectly except I can’t see the months which doesn’t have data. what I am expecting If a month doesn’t have data price should be 0.

List<decimal> osman1 = osman.GroupBy(i => new 
{ 
    Field1 = i.Field<DateTime>("CreateDate").Month 
})
.Select(group => group.Sum(i => Convert.ToDecimal(i["Price"])))
.ToList();

result osman1 is

{221,103,352}

what I need is

{0,0,0,0,0,0,0,221,0,103,352,0}

Answer 1

The simplest way is probably to do a group join:

var totalsByMonth = Enumerable.Range(1, 12)
      .GroupJoin(osman,
                 month => month,
                 record => record.Field<DateTime>("CreateDate").Month,
                 (month, records) => records.Sum(r => r.Field<decimal>("Price")))
      .ToList();

(I’ve used Field<decimal> rather than Convert.ToDecimal as I think it’s usually cleaner; change it if you need to, of course.)