Why does List implement IReadOnlyList in .NET 4.5?

Question

Why does List implement IReadOnlyList in .NET 4.5?

List isn\'t read only...

Answer 1

Isn't it true that the code running IReadOnlyList(Of T) calls to an object that implements that interface is usually running the same thread of execution. That prevents the object from being altered by itself, unless its running on a different thread of execution, but for that situation we have synchronization calls to solve that.