Can a .NET update/hotfix pull the rug from under my program's feet?

Question

Say I deploy a .NET application, and Microsoft issues an update or a hotfix that changes the behavior of the .NET layer. Could this affect the predictability of my code, causing it to behave in an unintended manner, if my code is relying on some specific output or side effect of a given .NET method or component?

And can I force my code to use a certain version/build of the .NET layer so that if my customer updates his .NET layer, my code continues to use the old one?

Am I being paranoid or is this a legitimate concern regarding something that has happened in the past?

Answer 1

Yes, key hotfixes have been known to effect programmes, not just .NET. That being said the likelyhood is really low, hotfixes might stop a non-standard or hacker approach, but won't touch the mainstream stuff. Build a unit-test suite, and test your code as you get each KB - release patches if you find something's failed (which you probably never will, but you'll have peace of mind :)).

Answer 2

Microsoft holds a very strict backwards-compatibility standard so that they can reduce the impact of upgrades as much as possible, for that reason it is very unlikely that a hotfix or patch would break any existing code. Although it is a possibility, the likelihood of it happening is very low and not usually worth stressing over.

As Rudi said, for added security you can use unit testing to ensure this sort of thing isn't happening.