Select distinct using linq
Using morelinq you can use DistinctBy
:
myList.DistinctBy(x => x.id);
Otherwise, you can use a group:
myList.GroupBy(x => x.id)
.Select(g => g.First());
myList.GroupBy(test => test.id)
.Select(grp => grp.First());
Edit: as getting this IEnumerable<>
into a List<>
seems to be a mystery to many people, you can simply write:
var result = myList.GroupBy(test => test.id)
.Select(grp => grp.First())
.ToList();
But one is often better off working with the IEnumerable
rather than IList
as the Linq above is lazily evaluated: it doesn't actually do all of the work until the enumerable is iterated. When you call ToList
it actually walks the entire enumerable forcing all of the work to be done up front. (And may take a little while if your enumerable is infinitely long.)
The flipside to this advice is that each time you enumerate such an IEnumerable
the work to evaluate it has to be done afresh. So you need to decide for each case whether it is better to work with the lazily evaluated IEnumerable
or to realize it into a List
, Set
, Dictionary
or whatnot.