In the old days there were arrays. Basic gave you dynamic arrays that could be redimensioned, even while preserving their data. This was expensive, but it would also be expensive to declare an array as large as you might ever need, and let most of it go wasted. C++ programmers came up with the linked list to solve this problem.

We've come a long way since then. There are linked lists, hash tables, arrays, sorted dictionaries, and the like. In the .NET world, we have typed (generic, like from templates) and untyped (System.Object with boxing and unboxing) collections.

Which ones do you find yourself using regularly?

I find myself using List<T>, Dictionary<T,T> and ObservableCollection<T> like it's going out of style. I love those and can't imagine what I ever did with out them or LINQ.

I tend to use my own collection that decorates a Dictionary<T, T> and List<T> myself. Depending on the situation, I usually need to get at an item either by its key or ordinal, and both of these support one or the other. SortedList<T> offers both, but the performance hit compared to hashing is too much.

I tend to use either a List<> where im not fussed about being able to do a lookup or a Hashtable where I need to be able to do a lookup.

I would probably have shot myself a long time ago without these two.

i liek to collect domains is that eligible? hehe

Domains of objects, or swamp domains, like the frog who climbed the reed and said "This is my domain - I'm king of all I see?"

I find myself using a List in almost every single program I write. It is a good approximation for a real world list and can be easily databound to UI elements. I used a dictionary for the first time the other day, and it seems to work out pretty well, also. I might try to use them more when the situation calls for mapping one thing to another.

List, Hashtable, Dictionary and NameValueCollection for me.