Linq Select why am I getting a result?

Question

I am getting a very strange result with my linq query that I don't understand:

public class Person 
{
    public Address Address { get; set; }
    public string Name { get; set; }
    ...
}

Imagine that I have a ICollection<Person> with one entry and that person is having a Address null

When I do the following linq statement:

var test = person.Select(x => x.Address).ToList();

the test variable is a List with 1 entry which is null.

• Why exactly do I get one null entry instead of an empty list?
• What would I have to change to get an empty list?

Thanks in advance

Answer 1

Why exactly do I get one null entry instead of an empty list?

Because Select is a projection and it will give just the result of adress so null

From MSDN

Projects each element of a sequence into a new form.

What would I have to change to get an empty list?

 var test = person.Where(x => x.Address != null).Select(x => x.Address).ToList();

or in LINQ Query Expression

var t = from p in person
                where p.Adresse != null
                select p.Adresse;

Answer 2

Add a where statement to limit the results so that it contains only persons for which address is not null:

var test = person.Where(x => x.Address != null).Select(x => x.Address).ToList();

If you don't do this, your results are not filtered and you just get back a projection of all elements in the collection.