By looking at the documentation, between .NET Framework v4.0 and v4.5 the List<T> started implementing the IReadOnlyCollection<T> interface. The documentation of IReadOnlyCollection<T> says:
Represents a strongly-typed, read-only collection of elements.
I am confused on why List implements such an interface. After all, can't the list items be modified? I think I am likely misinterpreting the meaning of "read-only collection" in this context, but I do not understand how. For example, as the MSDN documentation states for the ReadOnlyCollection<T> class:
A collection that is read-only is simply a collection with a wrapper that prevents modifying the collection; therefore, if changes are made to the underlying collection, the read-only collection reflects those changes.
The ReadOnlyCollection<T> class in fact does not allow, for instance, to Add elements.
Furthermore, in later versions of .NET, some types have been introduced which are explicitly for immutable lists:
IImmutableList<T>interface although introduced much later, in .NET 6.- For the class
ImmutableList<T>, the documentation says: When you add or remove items from an immutable list, a copy of the original list is made with the items added or removed, and the original list is unchanged. - The
ImmutableArray<T>struct is another example.
Any clarification is appreciated.