ReadOnlyExtensions (nuget): Extensions to expose lists, collections, dictionaries, and enumerables as read-only.  IList<T>.AsReadOnly() ICollection<T>.AsReadOnly() IDictionary<TKey,TValue>.AsReadOnly() IEnumerable<T>.AsReadOnly()
Keywords: system|generic|read|only|list|lists|dictionary|dictionaries|collection|collections|readonly|readonlycollections|readonlyextensions