IList and IReadOnlyList

Question

If I have a method that requires a parameter that,

• Has a Count property
• Has an integer indexer (get-only)

What should the type

Answer 1

What you need is the IReadOnlyCollection available in .Net 4.5 which is essentially an IEnumerable which has Count as the property but if you need indexing as well then you need IReadOnlyList which would also give an indexer.

I don't know about you but I think this interface is a must have that had been missing for a very long time.