c# - Generics vs. Array Lists

Question

The system I work on here was written before .net 2.0 and didn't have the benefit of generics. It was eventually updated to 2.0, but none of the code was refactored due to time constraints. There are a number of places where the code uses ArraysLists etc. that store things as objects.

From performance perspective, how important change the code to using generics? I know from a perfomance perspective, boxing and unboxing etc., it is inefficient, but how much of a performance gain will there really be from changing it? Are generics something to use on a go forward basis, or it there enough of a performance change that a conscience effort should be made to update old code?

Answer 1

Technically the performance of generics is, as you say, better. However, unless performance is hugely important AND you've already optimised in other areas you're likely to get MUCH better improvements by spending your time elsewhere.

I would suggest:

• use generics going forward.
• if you have solid unit tests then refactor to generics as you touch code
• spend other time doing refactorings/measurement that will significantly improve performance (database calls, changing data structures, etc) rather than a few milliseconds here and there.

Of course there's reasons other than performance to change to generics:

• less error prone, since you have compile-time checking of types
• more readable, you don't need to cast all over the place and it's obvious what type is stored in a collection
• if you're using generics going forward, then it's cleaner to use them everywhere