Best practice: ref parameter or return value?

Question

Actually I am doing a list as a reference parameter as follows:

public static List ListMethod(List result)

I saw some people doing in this

Answer 1

If you're just returning a List, you should always use the first one as it shows that intention.

The version with ref tells me that I can start out with a list, and your method will modify the list I sent in, or even change it with another one. If that is your intention, do that.

But if the method allways returns a new list, use a return value instead of a ref parameter.

A note on the side: you could use out instead of ref to show your intentions of returning a new list, but this is only a good practice if you're using the return value for something else.