How to get the Max() of a Count() with LINQ

Question

I'm new to LINQ and I have this situation. I have this table:

ID Date  Range
1 10/10/10 9-10
2 10/10/10 9-10
3 10/10/10 9-10
4 10/10/10 8-9
5 10/11/10 1-2
6 10/11/10 1-2
7 10/12/10 5-6

I just want to list the Maximun of rows per date by range, like this:

Date  Range  Total
10/10/10 9-10  3
10/11/10 1-2  2
10/12/10 5-6  1

I want to do this by using LINQ, do you have any ideas of how to do this?

Answer 1

I think something along these lines should work:

List<MyTable> items = GetItems();
var orderedByMax = from i in items
                   group i by i.Date into g
                   let q = g.GroupBy(i => i.Range)
                            .Select(g2 => new {Range = g2.Key, Count = g2.Count()})
                            .OrderByDescending(i => i.Count)
                   let max = q.FirstOrDefault()
                   select new {
                      Date = g.Key,
                      Range = max.Range,
                      Total = max.Count
                   };

Answer 2

Using extension methods:

List<MyTable> items = GetItems();

var rangeTotals = items.GroupBy(x => new { x.Date, x.Range }) // Group by Date + Range
                  .Select(g => new { 
                              Date = g.Key.Date, 
                              Range = g.Key.Range, 
                              Total = g.Count() // Count total of identical ranges per date
                              });

var rangeMaxTotals = rangeTotals.Where(rt => !rangeTotals.Any(z => z.Date == rt.Date && z.Total > rt.Total)); // Get maximum totals for each date