What does Random(int seed) guarantee?

Question

I'm working on a project, that relies assigning users random (nothing fancy, just uniformly) subsets of a larger set. Each user has a unique identifier from a set isomorphic to integers. There are two approaches to doing this, as far as I can see.

1. Create a database junction table between users and keyed elements of the aforementioned larger set with some function once for each user. This can be somewhat impractical for my needs, so I would rather do...
2. At run-time determine the subset by a similar function but use the unique user id as seed value, and just have the set in memory. Next time it's needed it's created again, from a larger set.

So my question is, if I use the .NET Random object to create the second function using user-id as a seed value, does Microsoft guarantee not to change the Random algorithm in the future? I.e. will all new Random(n)'s Next() sequences be the same forever on all machines?

Alternatively I could create my own random generator, and package it with my code. In fact, this is what I'll probably do, but I'm still curious to know the answer.

Answer 1

No, it is explicitly not guaranteed to be compatible across versions:

The implementation of the random number generator in the Random class is not guaranteed to remain the same across major versions of the .NET Framework. As a result, your application code should not assume that the same seed will result in the same pseudo-random sequence in different versions of the .NET Framework.