Given Prime Number N, Compute the Next Prime?

Question

A coworker just told me that the C# Dictionary collection resizes by prime numbers for arcane reasons relating to hashing. And my immediate question was, \"how does it know

Answer 1

Just in case somebody is curious:

Using reflector I determined that .Net uses a static class that contains a hard coded list of ~72 primes ranging up to 7199369 which is scans for the smallest prime that is at least twice the current size, and for sizes larger than that it computes the next prime by trial division of all odd numbers up to the sqrt of the potential number. This class is immutable and thread safe (i.e. larger primes are not stored for future use).