Why does default == implementation not call Equals? [duplicate]

Question

Possible Duplicate:
Why ReferenceEquals and == operator behave different from Equals

The default implementation of == operator compares objects by references. So when you override Equals (which default behaviour is the same) you have to also specify == and != operators so that they call Equals (and make it in every class of hierarchy as == and != operators are not virtual).

My question is why it is so? Why does == and != compare objects by reference instead of using Equals? I guess there should be a reason for such a fundamental thing.

Update.

To comments: I assumed == should depend on Equals (but not vice versa) as you can override Equals in base class and use this implementation in derived classes automatically. It wouldn't work if Equals used == in its implementation, as == is not virtual.

Answer 1

I believe the main reason is == is a static operator and can be called on null objects while Equals requires an instance.

For example:

Foo foo1 = null; Foo foo2 = null;  Console.WriteLine(foo1 == foo2); // cannot use Equals 

Answer 2

Object.ReferenceEquals is a static member that compares reference equality. Even value types are boxed before being passed to that method.

What about Equals, it's a virtual method, which means it lets to a consumer to override a functionality.

So default implementation of == behavior presumes default comparison(reference) is ok for you, if you need something specific, in this case framework provides you with a virtual method, which can be overriden.