When can a == b be false and a.Equals(b) true?

Question

I ran into this situation today. I have an object which I\'m testing for equality; the Create() method returns a subclass implementation of MyObject.

MyObject         


        

Answer 1

The "==" operate tests absolute equality (unless overloaded); that is, it tests whether two objects are the same object. That's only true if you assigned one to the other, ie.

MyObject a = MyObject.Create();
MyObject b = a;

Just setting all the properties of two objects equal doesn't mean the objects themselves are. Under the hood, what the "==" operator is comparing is the addresses of the objects in memory. A practical effect of this is that if two objects are truly equal, changing a property on one of them will also change it on the other, whereas if they're only similar ("Equals" equal), it won't. This is perfectly consistent once you understand the principle.