Which is better to use array or List<>? [duplicate]

Answer 1

More context is really required to answer the question properly:

In a public API, you should try to use abstract collection types, so that you can change the internal implementation later if you need to.

• If the collection should not be changed by the outside world, use IEnumerable.
• If the collection will be changed by the outside world, use ICollection.
• If indexed access is required, use IList.

In a private implementation, it's not as important to use the abstract types:

• If you need indexed access and know the final size, use T[] or List.
• If you need indexed access and don't know the final size, use List.
• If you plan to access elements in a LIFO pattern, use Stack.
• If you plan to access elements in a FIFO pattern, use Queue.
• If you need to access elements at the beginning and end of the list, but not in the middle, use LinkedList.
• If you don't want duplicates, use HashSet.

In .NET 4.0 you have a few more choices, but those are the basics.