GetHashCode override of object containing generic array

Question

I have a class that contains the following two properties:

public int Id      { get; private set; }
public T[] Values  { get; private set; }

<

Answer 1

Since the hashCode is kinda a key for storing the object (lllike in a hashtable), i would use just Id.GetHashCode()

Answer 2

public override int GetHashCode() {
   return Id.GetHashCode() ^ Values.GetHashCode();  
}

---

There are several good points in the comments and other answers. The OP should consider whether the Values would be used as part of the "key" if the object were used as a key in a dictionary. If so, then they should be part of the hash code, otherwise, not.

On the other hand, I'm not sure why the GetHashCode method should mirror SequenceEqual. It's meant to compute an index into a hash table, not to be the complete determinant of equality. If there are many hash table collisions using the algorithm above, and if they differ in the sequence of the Values, then an algorithm should be chosen that takes sequence into account. If sequence doesn't really matter, save the time and don't take it into account.

Answer 3

FWIW, it's very dangerous to use the contents of the Values in your hash code. You should only do this if you can guarantee that it will never change. However, since it is exposed, I don't think guaranteeing it is possible. The hashcode of an object should never change. Otherwise, it loses its value as a key in a Hashtable or Dictionary. Consider the hard-to-find bug of using an object as a key in a Hashtable, its hashcode changes because of an outside influence and you can no longer find it in the Hashtable!