Use of AsReadOnly(); instead of [.. _events]

[ParsaMehdipour]

Is there a difference between using _events.AsReadOnly() and [.. _events]?

If yes why not use the first one?

[FasihUrRahman]

In C#, the difference between _event.AsReadOnly() and [..._event] involves how each creates a view of the original collection.

1. _event.AsReadOnly():
   • This method is called on a List<T> and returns a read-only wrapper for the list. The underlying data remains the same, but the wrapper prevents modification of the list (e.g., adding, removing, or changing elements) through the read-only view.
   • Changes to the original list still reflect in the read-only view, but any attempts to modify the list through the AsReadOnly() wrapper will throw a runtime exception.
   • It’s efficient because it doesn't copy the data, but only wraps the original list. Example: List _event = new List { 1, 2, 3 }; var readOnlyEvent = _event.AsReadOnly();
2. [..._event]:
   • If you're referring to creating a shallow copy of the list (like in some other languages, e.g., JavaScript), the C# equivalent would be new List<T>(_event). - Creating a new list like new List<T>(_event) would make a copy of the original list. The new list is independent of the original one, so changes made to one list don't affect the other. - This operation involves copying the entire list, which can have a performance impact depending on the size of the list. Example: List _event = new List { 1, 2, 3 }; List copiedEvent = new List(_event);

[ParsaMehdipour]

So the difference is that AsReadOnly() creates a wrapper which prevents modifications and the second one creates a copy of the list

What is the use case of each?