Overriding GetHashCode for mutable objects?

Question

I\'ve read about 10 different questions on when and how to override GetHashCode but there\'s still something I don\'t quite get. Most implementations of

Answer 1

If you have a mutable object, there isn't much point in overriding the GetHashCode method, as you can't really use it. It's used for example by the Dictionary and HashSet collections to place each item in a bucket. If you change the object while it's used as a key in the collection, the hash code no longer matches the bucket that the object is in, so the collection doesn't work properly and you may never find the object again.

If you want the lookup not to use the GetHashCode or Equals method of the class, you can always provide your own IEqualityComparer implementation to use instead when you create the Dictionary.

The Equals method is intended for value equality, so it's not wrong to implement it that way.