Why might a System.String object not cache its hash code?

Question

A glance at the source code for string.GetHashCode using Reflector reveals the following (for mscorlib.dll version 4.0):

public override unsafe int GetHashCo         


        

Answer 1

One more potential reason for this is that interned strings (specifically those that are added as shared readonly data by the compiler) can have exactly the same format as any other string. The fact that these strings are loaded into readonly memory means that those data pages can be shared easily across process, but that the it would not be possible to also have them cache a hashcode.

But as others have mentioned, the primary reason for not caching the value is that the additional memory usage is likely to far outweigh the potential savings of hashcode caching. The execution time of GetHashCode is O(N) on the length of the string so the worst case scenario of repeated hashing is well bounded.