Slight reformulation of cgeers answer to get you the tuples you want instead of arrays:
var combinations = from item1 in list
from item2 in list
where item1 < item2
select Tuple.Create(item1, item2);
(Use ToList
or ToArray
if you want.)
In non-query-expression form (reordered somewhat):
var combinations = list.SelectMany(x => list, (x, y) => Tuple.Create(x, y))
.Where(tuple => tuple.Item1 < tuple.Item2);
Both of these will actually consider n2 values instead of n2/2 values, although they’ll end up with the correct answer. An alternative would be:
var combinations = list.SelectMany((x, i) => list.Skip(i + 1), (x, y) => Tuple.Create(x, y));
… but this uses Skip
which may also not be optimized. It probably doesn’t matter, to be honest – I’d pick whichever one is most appropriate for your usage.