Easy way to initialise array of reference types?

Question

By default, an array of reference types gets initialised with all references as null.

Is there any kind of syntax trick to initialise them with new default objects instead?

eg

public class Child
{
}

public class Parent
{
    private Child[] _children = new Child[10];

    public Parent()
    {
        //any way to negate the need for this?
        for (int n = 0; n < _children.Length; n++)
           _children[n] = new Child();
    }
}

Colicweed

No, just the obvious ways to hide the loop (putting it in a helper method, etc.). – Minuet

+1 for pointing out that you want a syntax trick, not what most people ask for - "can I do this without iterating the array?". However, I assume you want to maintain some sort of readability and actually be able to tell - at a glance - what the code does. =) – Vitrescent

Answer 1

Use LINQ:

 private Child[] _children = Enumerable
                                 .Range(1, 10)
                                 .Select(i => new Child())
                                 .ToArray();

Angeloangelology

Answer 2

You could use object and collection initializers, though your version is probably terser and can be used as is for larger collections:

private Child[] _children = new Child[] { 
new Child(),
new Child(),
new Child(),
new Child(),
new Child(),
new Child(),
new Child(),
new Child(),
new Child()
};

Crowl

Answer 3

Even if your for loop looks worse, than the nice LINQ statement the runtime behavior of it will be much faster. E.g. a test with 20 Forms in an array is 0.7 (for loop) to 3.5 (LINQ) milliseconds

Devotee

But often, we don't care. Still there is a good warning not to use LINQ for everything. – Footless

Answer 4

You could use Array.Fill method:

public static void Fill<T> (T[] array, T value);

public class Child
{
}

public class Parent
{
    private Child[] _children = new Child[10];

    public Parent()
    {
        Array.Fill(_children, new Child());
    }
}

Unmusical

Note that this is .Net >= 5.0 only. It is also less useful for reference types since it fills the array with the same instance. However, useful to know it's an option, so thank you! – Colicweed