Linq To Sql Count By Time Brackets

Question

I need a Linq To SQL Query that Counts the rows of a table that fall within time brackets of an arbitrary interval. The Table has a single DateTime field.

Google got me to this SQL (http://ebersys.blogspot.ca/2010/12/sql-group-datetime-by-arbitrary-time.html)

    declare @interval int
    set @interval = 5
    select convert(varchar(8), DTColumn, 1)+' '
    +convert(varchar(2), datepart(hh, DTColumn))+':'
    +convert(varchar(2), datepart(mi, DTColumn)/@interval*@interval)
    , count(*)
    from the_table
    group by convert(varchar(8), DTColumn, 1)+' '
    +convert(varchar(2), datepart(hh, DTColumn))+':'
    +convert(varchar(2), datepart(mi, DTColumn)/@interval*@interval)

I could move the query to SQL but prefer to keep the DAL consistent LinqToSQL. The best I could come up with is this, but errors with "Tick is not supported in SQL"

    int interval = Convert.ToInt32(uxTxtInterval.Text);
    var q = (from d in dc.theTable.OrderBy(o => o.dmMe).ThenBy(o => o.dmWith).ThenBy(o => o.dmCreatedAt)
          group d by
          (
               Math.Floor(new TimeSpan(d.dmCreatedAt.Ticks).TotalMinutes / interval)
          )
          into grpTable
          select
                new
                {
                  time = grpTable.Key,    // ?? needs to be the DateTime not ticks
                  count = grpTable.Count()
                 }
          );

Any help greatly appreciated :-)

Thanks!

Answer 1

You can use SqlMethods.DateDiffMinute to get the time buckets:

var startdate = new DateTime(1900,1,1); // An arbitrary date
int interval = Convert.ToInt32(uxTxtInterval.Text);
var q = (from d in dc.theTable.OrderBy(o => o.dmMe).ThenBy(o => o.dmWith).ThenBy(o => o.dmCreatedAt)
      group d by
      (
           SqlMethods.DateDiffMinute(startdate, d.dmCreatedAt) / interval
      )
      into grpTable
      select
            new
            {
              time = grpTable.Key, 
              count = grpTable.Count()
             }
      );