Performing and type-safe collection of value types in the early version of .NET

Question

I recently got access to a very old C# code base (very old meaning .NET 1.1 and C# 1.2) in order to find places that could be improved. It is like a window to the past when a bow was the most powerfull weapon. I have never had the opportunity to willingly code in C# version lesser than C# 2 before.

Basically, what I have found is that there is a whole bunch of large ArrayLists for storing numbers and structs. By large I mean tens or hundreds of thousand of values. Something like

ArrayList numbers = new ArrayList();
for(int i = 0; i < BIG_CONSTANT; i++)
    numbers.Add(someNumberReturnedFromMethod);

These lists are sorted on some place then again sorted by a different standard on another place, or there are searches performed on them.

Knowing that ArrayList works with objects results in two problems I came up with

• no type-safety
• boxing and unboxing everywhere

So the question is, how to solve this without the aid of generics? I definitely will not make classes from these structs in order to remove un/boxing, because with so many data, this really makes difference (tested).

I thought about creating custom array lists that would work with my structs instead. Do I have to create a custom array list implementation for every struct there is? Thinging about it, it would mean to define my own IEnumerable, ICollection and IList for each of these structs, right?

I think that it could be a good cost to pay in order to get more performing and type-safe system, but before trying it out I would like to know your opinion.

Answer 1

Without generics you cannot create a collection that avoids boxing with value types. But you can create specialized collections for concrete value types.

Here's an idea: Create your own version of ArrayList but use T4 templates to generate specialized versions for every concrete type you care about. That gives you, without code duplication, an ArrayListInt32, an ArrayListSingle and so on.

This removes any performance penalty from the boxing and restores type safety.

Actually, Java has a similar problem because due to type erasure they cannot use generics to avoid boxing. They do have some specialized array list classes in newer versions. Thank god C# does implement true generics in recent versions.