Can I have List(T).ForEach() that traverses elements strictly in order?

Question

There's List(T).ForEach() that performs an action on each element of the list. However MSDN description doesn't say anything about the order in which List elements will be traversed and I need to have them traversed strictly in order.

How can I achieve that with ForEach()?

Answer 1

List<T>.ForEach will go in the same order as a normal foreach loop, which is also the natural order of the list.

Yes, the documentation doesn't state it - but it's the obvious behaviour, and I think it's pretty reasonable to rely on that not changing.

(Now Parallel.ForEach is a different matter, of course.)

Answer 2

If the order of the elements is essential I would recommend to use a Queue<T> (LIFO) or a Stack<T> (FIFO) which ensure the order by design. In this case you have to use a classic loop instead using the LINQ extension method or implement it by yourself.

Answer 3

The List<T> class represents an ordered collection of items, so iterating it using enumerators or ForEach method will preserve the order, even if the documentation is not very clear on this.