LINQ: Distinct values
distinct, linq
Solution
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.)
Problem
I have the following item set from an XML: ``` id category 5 1 5 3 5 4 5 3 5 3 ``` I need a distinct list of these items: ``` 5 1 5 3 5 4 ``` How can I distinct for Category AND Id too in LINQ?