What should a function return?

Question

Let's say I have a function like this:

public List<int> func()
{}

Now, for some reason I don't have anything to put into the list, so I will just be returning "something empty". According to a good practice, which one of the following three should I return in the function above?

return null;
return new List<int>();  
return default(List<int>);  //Is this the same thing as the one above?

Answer 1

Return an empty list:

return new List<int>();

The default(List<int>) will return null; not an empty list!

Returning an empty list prevents excessive null checking after each call to your function. See Is it better to return null or empty collection?

Answer 2

Return an empty list. When you return null, you have to check that condition in the code that called func.