ArrayList vs List<> in C#

c# .net list generics arraylist
scatman picture scatman · Feb 22, 2010 · Viewed 387.8k times · Source

What is the difference between ArrayList and List<> in C#?

Is it only that List<> has a type while ArrayList doesn't?

Answer

Mehrdad Afshari picture Mehrdad Afshari · Feb 22, 2010

Yes, pretty much. List<T> is a generic class. It supports storing values of a specific type without casting to or from object (which would have incurred boxing/unboxing overhead when T is a value type in the ArrayList case). ArrayList simply stores object references. As a generic collection, List<T> implements the generic IEnumerable<T> interface and can be used easily in LINQ (without requiring any Cast or OfType call).

ArrayList belongs to the days that C# didn't have generics. It's deprecated in favor of List<T>. You shouldn't use ArrayList in new code that targets .NET >= 2.0 unless you have to interface with an old API that uses it.

Related questions

How to initialize a List<T> to a given size (as opposed to capacity)?

.NET offers a generic list container whose performance is almost identical (see Performance of Arrays vs. Lists question). However they are quite different in initialization. Arrays are very easy to initialize with a default value, and by definition they already …

Read More
Generic List - moving an item within the list

So I have a generic list, and an oldIndex and a newIndex value. I want to move the item at oldIndex, to newIndex...as simply as possible. Any suggestions? Note The item should be end up between the items at (…

Read More
Does .NET have a way to check if List a contains all items in List b?

I have the following method: namespace ListHelper { public class ListHelper<T> { public static bool ContainsAllItems(List<T> a, List<T> b) { return b.TrueForAll(delegate(T t) { return a.Contains(t); }); } } } The purpose of …

Read More