Why is list when passed without ref to a function acting like passed with ref?

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It does not act like its passed by ref.

void ChangeMe(List<int> list) {
  list = new List<int>();
  list.Add(10);
}
void ChangeMeReally(ref List<int> list) {
  list = new List<int>();
  list.Add(10);
}

Try it. Do you notice the difference?

You can only change the contents of list (or any reference type) if you pass it without a ref (because as others have said, you are passing a reference to the object on the heap and thus change the same “memory”).

However you cannot change “list”, “list” is a variable that points to an object of type List. You can only change “list” if you pass it by reference (to make it point somewhere else). You get a copy of the reference, which if changed, can only be observed inside your method.

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