svick
commented
7 years ago When the object returned by this method is enumerated, Intersect yields distinct elements occurring in both sequences
Since it's the comparer that decides which elements are distinct, I think the behavior you see is correct.
To get the behavior you want, you can combine Where and Contains:
var li = las.Where(l => ld.Contains(l, cmp));(Though this approach is inefficient. If that matters to you, you might want to turn ld into a HashSet.)
toiiggww
terrajobst
https://github.com/Microsoft/referencesource/blob/7de0d30c7c5ef56ab60fee41fcdb50005d24979a/System.Core/System/Linq/Enumerable.cs#L763 class ClazzA { public int Int { get; set; } public char Char { get; set; } public string String { get; set; } } class ClazzAComparer : IEnumerable
{
public bool Equals(ClazzA x, ClazzA y)
{
return x != null & y != null ? ( x.String == y.String & x.Int == y.Int ) : x == null & y == null;
}
public int GetHashCode(ClazzA obj)
{
return obj.String.GetHashCode();
}
}
class MainClazz
{
static List las = new List{
new ClazzA { Int = 0, Char = 'a', String = 'str'},
new ClazzA { Int = 1, Char = 'a', String = 'str'},
new ClazzA { Int = 0, Char = 'b', String = 'str'},
new ClazzA { Int = 1, Char = 'b', String = 'str'}
};
void Main( )
{
ClazzAComparer cmp = new ClazzAComparer();
var ld = las.Distinct(cmp); // will be las[0] and las[1]
var li = las.Intersect(ld, cmp); // will be only las[0] and las[1] but I wish all of las
foreach (var i in li)
{
Console.WriteLine($"int {i.Int,-3}, char {i.Char,-3}, string {i.String,8}");
}
}
}
full demo project at https://github.com/toiiggww/IEnumerableIntersect