为什么ReferenceEquals（）比==更快

Question

I run the following code 10000 times(a and b are both instances of class C)

1.ReferenceEquals(a,b)  0.1 ms
2.a==b                  0.7 ms
3.a.Equals(b)           0.8 ms

Could you tell me why 1 is faster than 2 and 3...

Answer 1

It's hard to say without seeing any code, but:

This is probably because the class in question has implemented the == operator, so that it doesn't compare references. Instead it likely is comparing the contents of the object in some way, which will of course be substantially slower.

(The string class does this, for example.)