Question

Suppose you have a class Person :

public class Person
{
   public string Name { get; set;}
   public IEnumerable<Role> Roles {get; set;}
}

I should obviously instantiate the Roles in the constructor.
Now, I used to do it with a List like this :

public Person()
{
   Roles = new List<Role>();
}

But I discovered this static method in the System.Linq namespace

IEnumerable<T> Enumerable.Empty<T>();

From MSDN:

The Empty(TResult)() method caches an
empty sequence of type TResult. When
the object it returns is enumerated,
it yields no elements.

In some cases, this method is useful
for passing an empty sequence to a
user-defined method that takes an
IEnumerable(T). It can also be used to
generate a neutral element for methods
such as Union. See the Example section
for an example of this use of

So is it better to write the constructor like that? Do you use it? Why? or if not, Why not?

public Person()
{
   Roles = Enumerable.Empty<Role>();
}

Answer 1

I think most postings missed the main point. Even if you use an empty array or empty list, those are objects and they are stored in memory. The Garbage Collector has to take care of them. If you are dealing with a high throughput application, it could be a noticeable impact.

Enumerable.Empty does not create an object per call thus putting less load on the GC.

If the code is in low-throughput location, then it boils down to aesthetic considerations though.