LINQ: Distinct values
In addition to Jon Skeet's answer, you can also use the group by expressions to get the unique groups along w/ a count for each groups iterations:
var query = from e in doc.Elements("whatever")
group e by new { id = e.Key, val = e.Value } into g
select new { id = g.Key.id, val = g.Key.val, count = g.Count() };
Are you trying to be distinct by more than one field? If so, just use an anonymous type and the Distinct operator and it should be okay:
var query = doc.Elements("whatever")
.Select(element => new {
id = (int) element.Attribute("id"),
category = (int) element.Attribute("cat") })
.Distinct();
If you're trying to get a distinct set of values of a "larger" type, but only looking at some subset of properties for the distinctness aspect, you probably want DistinctBy
as implemented in MoreLINQ in DistinctBy.cs
:
public static IEnumerable<TSource> DistinctBy<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
IEqualityComparer<TKey> comparer)
{
HashSet<TKey> knownKeys = new HashSet<TKey>(comparer);
foreach (TSource element in source)
{
if (knownKeys.Add(keySelector(element)))
{
yield return element;
}
}
}
(If you pass in null
as the comparer, it will use the default comparer for the key type.)
Just use the Distinct()
with your own comparer.
http://msdn.microsoft.com/en-us/library/bb338049.aspx