list - Intersect between 2 collections in C# -

i have:

            list<infraestructura> l1 = listq1.tolist();             list<infraestructura> l2 = listq2.tolist(); 

and need intersect comparing ids. that:

 l1.intersect(l2, l1[].id_infraestructura == l2[].id_infraestructura)  

but don't know method must use , sintax.

i found this:

var ids = list1.select(a => a.id).intersect(list2.select(b => b.id)); 

but return list of ids , need list of elements contained in both lists.

thank you!

the other answers correct, can use intersect custom comparer. can create custom comparer implementing iequalitycomparer<> interface. , implementing interface must implmenet 2 methods, equals , gethashcode.

public class infraestructuracomparer: iequalitycomparer<infraestructura> {     /// <summary>     /// whether 2 infraestructura equal.     /// </summary>     public bool equals(infraestructura firstobj, infraestructura secondobj)     {         if (firstobj == null && secondobj == null)             return true;          if (firstobj == null || secondobj == null)             return false;          // equality logic goes here         return firstobj.id == secondobj.id;     }      /// <summary>     /// return hash code instance.     /// </summary>     public int gethashcode(infraestructura obj)     {         // don't compute hash code on null object.         if (obj == null) return 0;          unchecked         {             var hash = 17;              hash = hash * 23 + obj.id.gethashcode();              return hash;             }     } } 

and then:

var result = list1.intersect(list2, new infraestructuracomparer()); 

you can use comparer in except method, finding difference of 2 sequences.

var result = list1.except(list2, new infraestructuracomparer()); 

additionally:

from first point of view may misunderstood gethashcode(). can read method in many question of stackoverflow. can read answer question.