Question

I have a table with a datetime field. I want to retrieve a result set grouped by the month/year combination and the number of records that appear within that month/year. How can this be done in LINQ?

The closest I’ve been able to figure out is in TSQL:

select substring(mo,charindex(mo,'/'),50) from ( select mo=convert(varchar(2),month(created)) + '/' + convert(varchar(4), year(created))   ,qty=count(convert(varchar(2),month(created)) + '/' + convert(varchar(4), year(created))) from posts  group by convert(varchar(2),month(created)) + '/' + convert(varchar(4), year(created)) ) a order by substring(mo,charindex(mo,'/')+1,50) 

But I wouldn’t say that works…

Answer 1

var grouped = from p in posts      group p by new { month = p.Create.Month,year= p.Create.Year } into d      select new { dt = string.Format('{0}/{1}',d.Key.month,d.Key.year), count = d.Count() }; 

Here’s the list of DateTime functions available in LINQ. For this to work you’ll also need to understand multi-column grouping

ordered descending

var grouped = (from p in posts    group p by new { month = p.Create.Month,year= p.Create.Year } into d    select new { dt = string.Format('{0}/{1}',d.Key.month,d.Key.year), count = d.Count()}).OrderByDescending (g => g.dt);