Why GetHashCode is in Object class?

Question

Why GetHashCode is part of the Object class? Only small part of the objects of the classes are used as keys in hash tables. Wouldn\'t it be better to have a separate interfa

Answer 1

Only small part of the objects of the classes are used as keys in hash tables

I would argue that this is not a true statement. Many classes are often used as keys in hash tables - and object references themselves are very often used. Having the default implementation of GetHashCode exist in System.Object means that ANY object can be used as a key, without restrictions.

This seems much nicer than forcing a custom interface on objects, just to be able to hash them. You never know when you may need to use an object as the key in a hashed collection.

This is especially true when using things like HashSet<T> - In this case, often, an object reference is used for tracking and uniqueness, not necessarily as a "key". Had hashing required a custom interface, many classes would become much less useful.