Probability of getting a duplicate value when calling GetHashCode() on strings

Question

I want to know the probability of getting duplicate values when calling the GetHashCode() method on string instances. For instance, according to th

Answer 1

I think all that's possible to say is "small, but finite and definitely not zero" -- in other words you must not rely on GetHashCode() ever returning unique values for two different instances.

To my mind, hashcodes are best used when you want to tell quickly if two instances are different -- not if they're the same.

In other words, if two objects have different hash codes, you know they are different and need not do a (possibly expensive) deeper comparison.

However, if the hash codes for two objects are the same, you must go on to compare the objects themselves to see if they're actually the same.